Using An Option Group

I am trying to open a report linked to a query from a form with an option group, so as to select specific records, but I keep getting the error message object required, queries!qryCost!North_South =<Object required>
The code in VBA is as follows:

Dim stDocName, WClause As String
stDocName = "rptCost"
WClause = "[North_South]= " & Chr(39) & queries!qryCost!North_South = North

Select Case fraSelect
Case 1
DoCmd.OpenReport stDocName, acPreview
Case 2
DoCmd.OpenReport stDocName, acPreview, , WClause

End Select

What am I doing wrong?
Thanks JenniD