Cells(Row,16) is a date formatted 02/13/04

Worksheets(4).Cells(10, 5) = DateDiff("d", Date, Cells(Row,16) Doesn't work.

I tried
dim billed as date
billed = cells(row,16)
datediff("d",date, billed)
but that doesn't work either.

I need the difference in days between two dates. One is cells(row, 16)
and the other is today's date. I imagine it has something to do with how
the dates are formatted but I can't find anything about it.

Thanks

John