It's hard for me to determine how to help without seeing your script, but maybe this will help.
How is the validation script triggered, and what field are you on when it does? I think if you start on the field you want to end up on (amount field), trigger the script there, and put in Exit Script [False], you should end up back where you started.
I haven't used the Exit Script function before, but that acutally made the trick. Thanks a lot!
Just to complete the information I was already triggering the event in the 'amount' field with an OnObjectValidate-trigger.
Thanks for your help.