Filter Criteria

I have a form that is opened filtered based on the selection of a ComboBox based on the following code.

Now I want to futher restrict the data that is shown when the form opens by showing;
a) only those records where [DelDate] is null, and
b) only those records where [Deldate] is null or [Deldate] > date()-2

I know it has to be incorpoprated into stLinkCriteria I'm just not sure on the syntax and structure

Thanks in advance and sorry for the simple question :o

Private Sub Command3_Click()
On Error GoTo Err_Command3_Click

Dim stDocName As String
Dim stLinkCriteria As String

stDocName = "FRM_AWMPonum"

stLinkCriteria = "[ClientID]=" & Me![Combo0]
DoCmd.OpenForm stDocName, , , stLinkCriteria

Exit_Command3_Click:
Exit Sub

Err_Command3_Click:
MsgBox Err.Description
Resume Exit_Command3_Click

End Sub