Use Data Validation:

Let's say the largest value we want in B1 is 100 and we do not want A1
changed if B1 is equal to or greater than 100.

Click on A1 and:

Data Validation... Custom Formula
=B1<100

Note that this will work even if A1 and B1 are not directly related.
--
Gary''s Student - gsnu200780


"Ridhi" wrote:

1. I am trying to lock & unlock a cell depending upon a change in value of
the other cell.

2.Is there any way that we can desplay a user message or a error message if
a condition is not meet.