Thanks Dave,
I qualified the cell references in response to Alok's suggestion. I may have
done it incorrectly (pls see my response to him) because I am seeing the same
error.

In answer to your questions, yes Traffic Model is always the active sheet.
Rows is a (I admit) a poorly chosen variable. So I tried:
Dim YRng As Range
With Worksheets("traffic model")
Set YRng = .Range(.Cells(initial_blank_count - 1, initial_column + 7),
..Cells(Rows, initial_column + 7))
etc

but am still seeing the same error. Thanks for persisting with me, ... Greg