[GNC] Check for negative amount in scheduled transaction formula

[gnucash.dgr9z at ncf.ca]

Hi,

Is it possible to convert negative numbers to 0 in a formula? something like:
a-b < 0 ? 0 : a-b

If this needs to be defined as a function someplace, what would it look like, where would it go, and how would it be called from the template?

Many thanks,
Ron