Dependant variables - raising an Exception from a customer exit

Hi All,

I have a query with 5 variables. I am interested in 2 variables which I have to make dependant, that is, the user should be allowed to fill values for any one of them. If the user enters the value for both of them then I have to throw an error.

I have activated the customer exit and wrote the code for I_STEP = 3. I have populated the values from the two variables into 2 ranges objects and then performed a test for both not being initial. If this check qualifies then I am raising an Error Message.

The problem I am facing is the error message is not being displayed. Instead the connection breaks down with "SYSTEM ERROR". Can anyone suggest any work around or correct the approach I have taken.

What I do not understand is if I_STEP = 3 is for validating user input then how come the user be notified that his input is wrong?

Points will be rewarded.

Regards,

Kazmi