How can I make an error message pop up for a user?

[Can't do Macros]

I have a sheet with a list of employees that has percentages listed in 4
columns out from their name. How can I get an error message to pop up for
any row that doesn't equal 100% when you add up the 4 columns in each row?
Therefore, I want the macro to loop around so that it goes down the sheet
summing the 4 columns for each employee and an error message will pop when it
hits a row that doesn't equal 100%.

 

[Can''t do Macros]

Thanks for your help. I entered the code you gave me, but I get an error
message for the line that says vbCritical, "checking row sums"
The error message I get is: Compile error: Invalid use of property.

Do you have any tips for getting rid of this error message?

Thanks again!

 

[RB Smissaert]

Probably the linebreaks messing things up.
Put your cursor after:
100%!",
and press the Dell key a few times till you got vbCritical right after the
above.
Then try again.

RBS