So imagine you have a sample form that follows the format below;
____________________________________________________________
----------------------------TITLE OF FORM--------------------------
lblID txtID lblCompanyAddedOn dteIN
lblCompany txtCompanyName lblCriteriaFilter txtDateFilter
____________________________________________________________
Right click on the field that you have set to be the filter or criteria (in this example txtDateFilter).
Click on the Event Tab and click the [...] button on the row that says, "After Update", select Code. You will be brought to the VBE. There enter the following code.
(based on the example I drew up)
[VBA]
Private Sub txtDateFilter_AfterUpdate()
Me.Filter = "dteIn < " & txtDateFilter
Me.FilterOn = True
End Sub
[/VBA]
That should do it.