It does, I printed the value of 'y' just prior to the copy statemet
and this was '6' which is exactly the sheet I need in the source
workbook, you can also see in my code another print statement just
prior to the 'Copy' function - this prints the value of a cell (1,2)
in that sheet and also returns the correct data:-

MsgBox "CREATING NEW WORKSHEET FOR: " &
sourceBk.Worksheets(y).Cells(1, 2)
MsgBox "Y: " & y
sourceBk.Worksheets(y).Copy _
After:=wbMaster.Worksheets(wbMaster.Worksheets.Cou nt)

puzzling..