Hi Lewie,
The two easiest options you have are using
a. Filter
b. Criteria on forms source.
I am not sure how your table structure is set up so it's hard to give you a cut and paste solution. In the drop down box, I would have two columns. The first column would have the clients ID number, the second the clients name. The combo box would be bound to the first column, but would have zero width so it does not show up in the drop down box (just the name of the client).
In the OnClick event of the button (or the afterupdate event of the combo box), put something like:
Private Sub cmboID_AfterUpdate()
Dim ClientID As Integer
ClientID = Me.cmboID 'You would have to put the name of your combo box control name here.
DoCmd.OpenForm "frm_MyForm", , , "[ID] = ClientID" ' you would have to put the correct field name between the [] and put the correct name of your form.
End Sub
If your combo box will just hold text and in your new form you want the criteria on the client name field then you could use:
Private Sub cmboID_AfterUpdate()
Dim ClientName As String
ClientName = Me.cmbobox 'You would have to put the name of your combo box control name here.
DoCmd.OpenForm "frm_MyForm", , , "[Name] = '" & ClientName & "'" 'you would have to put the correct field name between the [] and put the correct name of your form.
End Sub