vba copy and paste based on multiple loop criteria

Hello I really need some help with my coding in Excel 2007.
I have 80 worksheets in my workbook. I am trying to evaluate each sheet so that if there is a "Y" in a certain range of worksheets ("M" for Monday), then that sheet's data will be pasted to the sheet that begins with P (for prior week). There are 10 of these PW1, PW2, etc.

Dim ws  As Worksheet
Dim ws1 As Worksheet

Application.ScreenUpdating = False


For Each ws In ActiveWorkbook.Worksheets
    If Left(ws.Name, 1) = "M" And ws.Range("B2").Value = "Y" Then   'evaluate if yes
        ws.Range("A4:R37").Copy
        ElseIf Left(ws1.Name, 1) = "P" And ws1.Range("A4").Value Is Null Then
        ws1.Range("a4").PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
        Application.CutCopyMode = False
    End If
Next ws
    Sheets("108 Compare").Select
    Range("A81").Select

Application.ScreenUpdating = True

the code fails on the ElseIf line.