Ragnar,
You don't say what you want if the values are not equal but the general
syntax for an IF statement is:
=IF(test, Do if test true, Do if test not true)
so in your case that would be:
=If(1st Column Value=2nd Column Value,Value from 3rd Column,Result if not
equal)
One caveat is if the 1st and 2nd values are determined by a calculation they
may differ by just a very small amount which would sop them being equal and
so you may have to round them before comparing.
HTH
Sandy