Its a root problem

Got a problem, with the root command in MX pro 2004.

I followed the tutorial on how to create increments in values using the root command.

But i keep getting the NaN returned, which i understand is that the dynamic text doesnt understand the value. I think its something simple wrong like a space or “”'s needed. The action script works in flash 5 but not in mx pro.

This is the tutorial http://www.kirupa.com/developer/mx/score.htm

this is the code -

on (release) {
_root.total = _root.total+100;
}

Would appreciate help - im no programmer, but am a multimedia student, seriously stuck on the last hurdle of my final product.

Many thanks for helpers.