In a message dated 15/10/2007 21:59:28 GMT Daylight Time, mike.brook@xxxxxxxxxxxxxx writes: Frank – Here you go … <g> _http://www.arachnoid.com/lutusp/calculator.html_ (http://www.arachnoid.com/lutusp/calculator.html) Cheers M. Mike, Sorry, what I meant I wanted was one that steps through XML reverse polish. The one I produced which doesn't work is - %((A:TOTAL FUEL QUANTITY, gallons)) 100 * %((A:FUEL TOTAL CAPACITY, gallons)) / % %3.1f!% which is meant to show current fuel percentage. If I could step through it I could spot where its going wrong! Frank T.