Javascript for a Validation

Hello again...

I have learned alot this week with incredible help from the community and I appreciate it.

I'm working on a field on PDF form and I'm trying to write a script for an amount that ends up as a negative number.  It seems the best way to address this would be to write a Validation script which would make the negative number return a 0 as the result.  Of course, the script that i came up with doesn't work.  It seems logical to think about doing it this way.  Here is Validation script that i attempted, if you have any thoughts that would once again be much appreciated.

if (event.value < 0) event.value = 0;