Excel must display error message if two blocks don't have same num

[Guest]

Version of Excel is 97
I have two columns - Start clock and stop clock - then next column has - total
in the next line if the End clock time from line before does not correspond
with Start clock time. - I must get an error message.

 

[Peo Sjoblom]

What do you mean by "correspond"? If one or more cells are empty?

=IF(COUNT(A2:B2)=2,B2-A2,"error message")

you might also want to look at data>validation

 

[Guest]

correspond - if two cells don't have exactly the same number, then error
message.
Thanks, I'm going to try your formula if this does not work I'll come back
to you for more info on - Data validation

 

[Peo Sjoblom]

Then try

=IF(B2<>B3,"error message",B3-A3)

 

[Guest]

Yes, thank you Peo. It works.

Then try

=IF(B2<>B3,"error message",B3-A3)