Worksheets("report").Cells(1, d).value = K(d)

(Not tested, but should be right.)

I don't think Worksheets has a Range member - if you want to specify
Worksheets as part of a range, they actually go inside the parentheses, as
part of the Range call's parameters. E.g.

Range (Worksheets("report").Cells(1, 1), Worksheets("report").Cells(1,
3)).etc