I have an excel formula where 3 columns (A,B, C) check values and if true, return "OK", I have a fourth column (D) where I want to check if all 3 columns contain "OK" then return text. I have tried various formulas and changing OK to blank and using ISBLANK formula but still not working. Can anyone please advise?

The formula in A,B C is =IF(A2 = "Cell Site Change - Implementers","OK","Missing Site Change IMP")

thank you.