HP Prime - Problem with the decimal separator

[wChris79]

Hello,
      I have a problem with the decimal separator. If I use the comma necessary to use the "fracmod ()" the program that contains the function no longer runs it stops on every point of the program, for example, list of variables etc ... And if I uses the period as the separator the program works except the "fracmod ()" which does not run because it forward a number with a comma and not a point.
How to define what functions to work with a point rather than a variable?
Thank you for your help.