I think I understand what you want to do here: but forgive me if I have
got the question wrong. You want to force the user to use a search form
before opening a form on that one record. What I do is this:

Create a search form: the top half of this has a couple of text boxes for
the stuff to search on, and a command button called search. The command
button runs code to create a SELECT query that uses the contents of the
text boxes, usually with LIKE operators rather than =. The results of
this query are displayed in a list box in the lower half, along with
command buttons OK and Cancel. Cancel unloads the form, OK simply hides
it. Other logic in the form caters for <new> record requests, etc. A
custom form method returns the selected value from the list box: more on
this later.

Create a Public Function that calls the search form in dialog mode. When
this returns, if the form is not loaded, then the user cancelled out, and
the function returns an error code. If the form is loaded and hidden,
then use the custom method to retrieve the requested record id, and
unload the form. If the requested record is a valid record, then return
that ID from the function. If it is the code for a <new> record, create a
new record and return a new identifier from the function.

OK so far?

The bit that actually works is calling the function from the Form_Open
event (of the main form). If the function returns the cancelled error,
then set the Cancel argument and Access will close the form before it
appears. If the function returns a valid record, then you create a sql
command like "select * from mytable where table_id = 10445" and poke it
into the RecordSource of the form.

The whole sequence is something like:

   DoCmd.OpenForm MainForm
 
->  Private sub Form_Open(Cancel as Integer) ' on Main Form
   
     dwRecordNum = GetARecordNumber()

->  public function GetARecordNumber() as Long

     docmd.Openform SearchForm

->  SearchForm is eventually hidden by user clicking "OK"

->  return to GetARecordNumber()

     If Not IsLoaded("SearchForm") Then
       ' user cancelled
       GetARecordNumber = -1

     ElseIf Forms!SearchForm.GetSelectedRecord = 0 Then
       ' <new> record requested
       GetARecordNumber = MakeANewRecord()
       DoCmd.Close SearchForm

     Else
       ' return the selected number
       GetARecordNumber = Forms!SearchForm.GetSelectedRecord
       DoCmd.Close SearchForm

     End If
       
       
->  back in Form_Open

     If dwRecordNum = -1 Then
       ' user cancelled
       Cancel = True
       Exit Sub

     Else
       strSQL = "SELECT * FROM MyTable WHERE TableID = " & dwRecordNum
       Me.RecordSource = strSQL

     End If

The smart thing to do then is put a command button called OK on the main
form, which calls the code a bit like this:

     ' relaunch the search form and get a new recordsource
     Call Form_Open(Cancel)  
 
     ' does the user want to stop doing this now?
     If Cancel = True then DoCmd.Close acForm, Me.Name

     ' otherwise it's just reopened on the new record anyway

It sounds a lot more complicated than it really is; but looks pretty
seamless to the user.

Hope it helps

Tim F