Allow numbers only AND add static text to final value?

*SOLVED* (see 2nd post)

I've spent the last 24 hours scouring the web for a solution to this problem without luck. I am trying to create a field on an Acrobat form that only allows numbers (and decimal) for input, and then formats the result with an added "WAS $" in front. I do not want the user to enter the dollar sign or the WAS text to enforce all forms created by various users to include the same wording.

Thanks to this site I was able to figure out that by adding
event.value = "WAS " + util.printf("$%,0.2f", event.value);
as a Custom Format Script, I could handle the addition of the "WAS $" static copy and format a valid value in a $#.## format.

Separately, I determined that by adding

var re = /[0-9.]/; 
if (re.test(event.change)) { 
  event.rc = true;
} else event.rc = false;

What doesn't seem to work is combining these two scripts to do both. If I use just the former code, an end user could attempt to enter alpha characters and/or symbols and get the result "WAS $nan". If I go with just the latter, I actually get nothing for a result? Can someone please steer me in the right direction to achieve the ultimate goal I need?

I am using Acrobat Pro 9.3.3 (not an option in forum dropdowns) on Mac OS X 10.6.3.