Thanks for testing,
i tried this
write the formula on row 29 and made a copy while filling with data
$oXL.Cells($i,13).formula = $oXL.Cells($i,29).formula
I have a sheet with 260 line and overite them every time with
aktuell data. But only to row 20. With this copy the same formula
is now in the field 13 and it works. I don't know why.
May be there a problems with the ' and " in the statement. But without the
= it works.

Thank Wolfgang