Why won't this routine run?

I can step through this routine, but when I try running it from Janaury 2009.xls it stops.

Sub CopyNew()
Workbooks.Open ("S:\shared\FORECAST\FmIncome\MTED Tables\Jan2009\WHEAT.xls")
 
 For i = 1 To 7
   For j = 1 To 2
     Workbooks("WHEAT.xls").Activate
       nwval = 0
         If Range("NewData").Cells(i, j).Value > 0 Then
            Set nwval = Range("NewData").Cells(i, j)
         End If
     If nwval > 0 Then
        Workbooks("January 2009.xls").Activate
        Range("DATA_WT").Cells(i, j) = nwval 
     End If
   Next j
 Next i
 End Sub