Code to check if Workbook Exists

[Jo15765]

I modified my code to:

Public Sub Monthly (varStar)
        On Error Resume Next
        Set WB = Workbooks.Open(Filename:="" & varStar)
        Call DoesWorkSheetExist       
        Run "RefreshOnOpen"
        With WB
            WB.SaveAs Filename:="" 
        End With
        WB.Close
        On Error GoTo 0
End Sub

I get a debug error of Argument not optional on the function posted here? Did I place it in the wrong place or leave out something?