Grouped Row Caption

I am using report control v. 10.3. I have noticed that when I update the group caption, the updated text disappears when the populate event is called, why? I have been able to get around the issue, but is there an easy way to keep this from occurring? Here is the code that I am using to perform the group caption update...

Dim sDoc As String
Dim rRow As ReportRow
Dim rGrp As ReportGroupRow

For Each rRow In Rpt_List.Rows
    If rRow.GroupRow Then
        Set rGrp = rRow
        If rGrp.Childs.count = 1 Then
            sDoc = " Document"
        Else
            sDoc = " Documents"
        End If
        rGrp.GroupCaption = rGrp.GroupCaption + " (" +   
        CStr(rGrp.Childs.count) + sDoc + ")"
    End If
Next
Rpt_List.Redraw

Thanks for the code. That works great.