hi, iam new to this abap.
my query is..
i have designed the selection screen with four fields all with select options.
in selection screen i hav to check the validity of the parameters and display error message if invalid input are made
and also display information message and leave processing the list if no material data could be found according to the selection criteria
these is mentioned in the functional spec
where should i write the code for the above 2 conditions
let me know as soon
thanks and regards.