Thanks for the quick reply.

I did try the application.volatile statement, unfortunately it did not
help.
But I have to say that I'm not sure where to place the statement. I
placed it in the beginning of the Function Naar_vergelijk.

For now, I redesigned the workbook so that it doesn't need to enter
formulas in the worksheet, and that the transportation of the data is
manually by a macro.

Still, it is a problem I've encountered several times now. And the
advantages of entering formulas in a worksheet by macro are too great
to let go, and I hope to find a "cure" someday before I'm old and
grey.

Frans