Dropdown List in Access for a Report

Hello again,
     I'm sure this is an easy question, and I have already had one very simular to it answered.  Here is a link to the last question like this one I posted: https://www.experts-exchange.com/questions/22061922/Dropdown-List-in-Access-for-a-Report.html

This time the dropdown will be selecting a number instead of a string.  Thank you in advance for your help.  Here is the code I'm trying to use, but of course I am getting a data type mismatch error, so please help me change it:

Option Compare Database
Option Explicit
Dim strFilter As String

Private Sub cmdOpenReport_Click()
DoCmd.OpenReport "rpt_weekly_group", acViewPreview, , strFilter
End Sub

Private Sub Detail_Click()

End Sub

Private Sub GruopID_AfterUpdate()
strFilter = ""

    If Me.GruopID <> "" And Not IsNull(Me.GruopID) Then
        If strFilter = "" Then
            strFilter = "[GruopID]= " & Chr(34) & Me.GruopID & Chr(34) & ""
        Else
            strFilter = strFilter & " and [GruopID]= " & Chr(34) & Me.GruopID & Chr(34) & ""
        End If
    End If
End Sub