Hallo everybody, i have programmed a sub procedure, that will be called in the main procedure (called by event of mainForm), to valid the inputs before the main calculation. now i'm searching for a method, how can i cancel the calculation and refocus the mainForm if some inputs mismatch. i think, it's unnecessary to use the Try-Catch statment to trap the error from calculation because i know what is its source and it should be prevented due to the code preformance. Has someone an idea to due with this? best regards Lert Pianapitham