No, you should not need to search through all 400 modules.

If you have functions that have the same names as VBA functions and want to
remove the functions all you need to know is the location (module) of the
same-named function.  Then you remove the same named function and the VBA
function will get called.

Personnally, I would comment out the function and then compile.  If no error
occurred after the compile, then I would delete the function.

Here is some code that can get you started.  Note that is does NOT search
class modules (forms and reports).  If you use it as is, you will need to
add a table to your database.

'TableName: tbl_ModuleList
'Fields:
'fldDBName - text
'fldModuleName - text
'fldProcName - text
'fldProcCall - text
'fldComments - Memo

'CODE FOLLOWS

Option Compare Database
Option Explicit

Public Function funListModules()
'*******************************************
'Name:      funListModules ()
'Purpose:   Open every module in the current database
'           and list the names of the Functions and Subroutines
'Author:    John Spencer UMBC-CHPDM
'Date:      10/3/2001
'*******************************************

Dim dbs As Database
Dim cntAny As Container
Dim docAny As Document
Dim intCount As Integer

  Set dbs = CurrentDb()
  Set cntAny = dbs.Containers("Modules")

  For intCount = 0 To cntAny.Documents.Count - 1
     Set docAny = cntAny.Documents(intCount)

     'Debug.Print "Module: " & docAny.Name
     If docAny.Name <> "basCrossRef" Then
        funListRoutines docAny.Name
     End If

  Next intCount

  Set docAny = Nothing
  Set cntAny = Nothing
  dbs.Close
  Set dbs = Nothing

End Function

Private Function fAddToTable(strDbName, strModule, strProc, _
                strCall, strComments)
'Adds procedure information to a table using an SQL statement
Dim strSQL As String, strCall1 As String
Dim strComments1 As String

  On Error GoTo fAddtoTable_ERROR

  strCall1 = strCall
  strComments1 = strComments & ""
  strComments1 = ReplaceString(strComments1, Chr(34), Chr(34) & Chr(34)) &
""
  If strComments1 = "" Then strComments1 = "No description"

  strSQL = "INSERT INTO tbl_ModuleList ( fldDBName, fldModuleName," & _
   " fldProcName, fldProcCall, fldComments )" & _
   "Values( " & Chr(34) & strDbName & Chr(34) & _
   ", " & Chr(34) & strModule & Chr(34) & _
   ", " & Chr(34) & strProc & Chr(34) & _
   ", " & Chr(34) & ReplaceString(strCall1, Chr(34), Chr(34) & Chr(34)) & _
   Chr(34) & _
   ", " & Chr(34) & strComments1 & Chr(34) & " )"

  CurrentDb().Execute strSQL, dbFailOnError

  Exit Function

fAddtoTable_ERROR:

  MsgBox "Err# " & Err.Number & ": " & Err.Description, , "fAddToTable"
  Stop

End Function

Private Function funListRoutines(strModule As String)
'Steps through a module and puts the name of its routines into a
'table along with the initial comments in the routine
Dim modAny As Module
Dim tfModuleOpen As Boolean
Dim lngLineCount As Long, lngCurrentLine As Long, lngProcKind As Long
Dim strProcName As String, strOutput As String, strCurrPosition As String
Dim strDbName As String, strCall As String, strComments As String

  strDbName = CurrentDb().Name
  strDbName = Dir(strDbName)

  If IsModuleOpen(strModule) = False Then
     DoCmd.OpenModule strModule
     tfModuleOpen = False
  Else
     tfModuleOpen = True
  End If

  Set modAny = Modules(strModule)

  lngLineCount = modAny.CountOfLines
  lngCurrentLine = 1

  While lngCurrentLine < lngLineCount

     strProcName = modAny.ProcOfLine(lngCurrentLine, lngProcKind)

     If strProcName <> "" Then
        strOutput = strProcName  'modany.Lines(lngCurrentLine, 1)

        While modAny.ProcBodyLine(strProcName, lngProcKind) <>
lngCurrentLine
           lngCurrentLine = lngCurrentLine + 1
           strOutput = strOutput & vbCrLf & _
                    Trim(modAny.Lines(lngCurrentLine, 1))
           strCall = Trim(modAny.Lines(lngCurrentLine, 1))
        Wend

        'Get Call string that is continued
        While Right(strCall, 1) = "_"
           lngCurrentLine = lngCurrentLine + 1
           strCall = Left(strCall, Len(strCall) - 1) & _
                    Trim(modAny.Lines(lngCurrentLine, 1))
        Wend

        lngCurrentLine = lngCurrentLine + 1

        strCurrPosition = Trim(modAny.Lines(lngCurrentLine, 1))

        strComments = ""
        While InStr(1, Trim(strCurrPosition), "'") = 1
           If Trim(ReplaceString(strCurrPosition, "=", "")) = "'" Then
           ElseIf Trim(ReplaceString(strCurrPosition, "*", "")) = "'" Then
           ElseIf Trim(ReplaceString(strCurrPosition, "-", "")) = "'" Then

           Else
              strComments = strComments & Trim(Mid(strCurrPosition, 2)) _
               & vbCrLf
           End If

           strOutput = strOutput & vbCrLf & strCurrPosition
           lngCurrentLine = lngCurrentLine + 1
           strCurrPosition = Trim(modAny.Lines(lngCurrentLine, 1))
        Wend

     End If

     'Output the data
     If Len(strProcName) > 0 Then
        fAddToTable strDbName, strModule, strProcName, _
                   strCall & "", strComments & ""
     End If

     'Step thru lines until we get to a new procedure
     'or we get to the end of the module
     While strProcName = modAny.ProcOfLine(lngCurrentLine, lngProcKind) _
                         And lngCurrentLine < lngLineCount
        lngCurrentLine = lngCurrentLine + 1
     Wend

  Wend

funListRoutines_EXIT:

  Set modAny = Nothing

  If tfModuleOpen = False Then
     DoCmd.Close acModule, strModule, acSaveNo
  End If

  Exit Function

funListRoutines_ERROR:
  Stop

End Function

Private Function IsModuleOpen(strModulename As String) As Boolean
'See if a module is already open
Dim modAny As Module

  On Error GoTo IsModuleOpen_ERROR
  Set modAny = Modules(strModulename)
  IsModuleOpen = True
  Exit Function

IsModuleOpen_ERROR:
  IsModuleOpen = False
End Function