I am assuming you want to populate the last of the 3 fields (mileage rate)? If so, use the calculate event in formCalc with something likevar changeDate = Date2Num( "2012-07-01", "YYYY-MM-DD" )var expenseDate = Date2Num( dteexpenseDate.rawValue, "YYYY-MM-DD" )var expenseTest = expenseDate - changeDa...