Filtering subform by main form combo

[diasflac]

I have a subform displaying a table of results.

I have used this code to have a combo box filter down the results:

Private Sub Combo5_AfterUpdate()
FindRFQsubform.Form.Filter = "[RFQ Title]= '" & Combo5 & "'"
FindRFQsubform.Form.FilterOn = True
End Sub

This works except I would like it to display all results from the query in the subform when I delete the selection out of the combo, as I have 4 combo's in total to be used to search a large amount of data.