Interface for editing formula

How should I go about creating an interface for editing a formula with a syntax like this?

%totalValueInUSD|round:1|add:100.5|formatAsPrice%

This would read the value from totalValueInUSD and round to 1 decimals and format is as price, and then add the value 100.

I've looked around, and personally I prefer something more programmer-friendly, something with a syntax highlight, and autocomplete support, but I'm biased, as I've been programming for a few years now, and this interface would be used by non-programmers, with no knowledge about computers.