Hello Anne,
I do not know if that answers your needs... but we have a similar question on fc cadlink for reduce a decimal number in an arithmetic expression and Eric Wilk had given quickly this way to solve the problem
if you have meter variables as x1 =1.565488855 and y1 = 3.9899898 for example and you want just two digits after the decimal point.
Try
round_int (x1 * 100) / 100
round_int (y1 * 100) / 100
The GDL Arithmetical Functions ROUND_INT (x) Returns the rounded integer part of x.
Maybe should help you ? Maybe a more elegant solution exist but you must wait for the response of people more qualified