Need help Referencing Other worksheets

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
For i = 1 To 18
Cells(i + 11, 7).Value = Application.VLookup("CFM", Worksheets("Sheet3").Range(Cells(35, 2), Cells(39, 19)), Application.Match(Cells(i + 11, 6), Worksheets("Sheet3").Range(Cells(35, 2), Cells(35, 19)), 0))
Cells(i + 11, 9).Value = Application.VLookup("HP", Range(Cells(35, 2), Cells(39, 19)), Application.Match(Cells(i + 11, 6), Range(Cells(35, 2), Cells(35, 19)), 0))
Cells(i + 11, 11).Value = Application.VLookup("AMP", Range(Cells(35, 2), Cells(39, 19)), Application.Match(Cells(i + 11, 6), Range(Cells(35, 2), Cells(35, 19)), 0))
Cells(i + 11, 12).Value = Application.VLookup("RPM", Range(Cells(35, 2), Cells(39, 19)), Application.Match(Cells(i + 11, 6), Range(Cells(35, 2), Cells(35, 19)), 0))
Next i
End Sub
w

I am very new to VBA, so I am encountering many issues trying to figure this out, but here's the first..
This is my code, Bolded portion is where the issue is... Code works fine when I am not trying to reference a different worksheet, but as soon as I do this it seems to get upset with me..

Oh, and Cells(i + 11, 11), this line appears to not be working correctly aside from being the exact same as the others...