Hello,

Array-enter in Excel 2007:
=IFERROR(MATCH(TRUE,C:C<0,0),"OK")

Any version before array-enter:
=IF(ISERROR(MATCH(TRUE,C:C<0,0)),"OK",MATCH(TRUE, C:C<0,0))

This will give an OK if and only if all values are 0 - or the row
number of the first cell < 0

Regards,
Bernd