One of my favorite functions doesn't work - really weird. When I get to line 50 of the workbook it stops working !!!! It doesn't matter if I cut n paste, drag or manually input the formulae it just stops ! Every row above row 50 - it works - below 50 ... nope #value appears. So an argument is wrong - but I'm inserting the same argument that works above !!!! Is this an Mac Office glitch or am I losing my mind Any advice appreciated . . . Stu edit: just realised that if I increase the lookup to row 75 the reference works up to row 75 but not beyond - weird. I can't replicate the problem on MS Office on a pc !