Can't figure out why EVAL isn't.

My form has detail section named Detail containing a text box named
MyTextControl.

Using properties window
Detail.OnMouseMove is set to  =OverAndOut("Detail")
MyTextControl.OnMouseMove is set to =OverAndOut("MyTextControl")

Over and Out is coded as such:
'====================================
Dim ControlNameMouseOver As String

Function OverAndOut(ControlName As String)
 Dim OutFunction As String
 Dim OverFunction As String
 Dim rc As Integer

 If ControlName <> ControlNameMouseOver Then
   OutFunction = ControlNameMouseOver & "_MouseOut()"

   On Error Resume Next
   rc = Eval(OutFunction)

   ControlNameMouseOver = ControlName

   OverFunction = ControlNameMouseOver & "_MouseOver()"
   rc = Eval(OverFunction)
 End If
End Function

Function MyTextControl_MouseOver() As Long
 MsgBox ("Over happened")
End Function

Function MyTextControl_MouseOut() As Long
 MsgBox ("Out happened")
End Function
'====================================

The OverAndOut code runs, but neither MyTextControl_MouseOver nor
MyTextControl_MouseOut runs.

Any reason why?

TIA,
Richard