Use 'if' to check a condition. If condition is not met, then do not change the value in the cell. Keep the previous value as it is

Cell B1 has value 1Cell B2 has value 1

Cell B10 has no value.I write 'if' formula: B10 = IF(b2=b1, b2,)The value in B10 changes to 1.

Now, I change B2 value to 2.The cell B10 changes to 0. (because the 'if' conditon is not met).

But I want the if forumula to do nothing and keep the B10 value same as before, i.e. 1. I do not want to change B10 value when 'if' condition is not met.

Please guide with the solution.