Bingo!
For some reason FormulaLocal solved the problem.
Thanks a lot!

Tamas

>>I also tried this:
>>

>>oExcel.ActiveSheet.Range("K22").Formula = "=SUM(K19;K16;K10;K7)"
>>

>>And I got this error message:
>>"OLE error code:0x800a03ec:Unknown COM status code"
>>
>>It may have sg. to do with the Hungarian version of Ms Excel?
>>I gonna check Naomi's links.
>>
>>Thanks again,
>>Tamas
>
>Try also to use FormulaLocal instead of Formula (suggested in another thread).
>
>Also, though irrelevant, perhaps you need to use cells in the different order, e.g. K7,K10,K16,K19.