We have several objects offer the user a group of roof slope selection parameters. You can select an n/12 slope from the list, or you can enter a custom slope angle. When you select a slope, the angle changes. When you put in an angle, the slope parameter will show n/12 if there is a match, and 'Custom' if not.
I use GLOB_MODPAR_NAME statements to keep such parameters in sync. In the code there are a bunch of IF/THEN statements associating the angles and the named slopes.
Since this lookup is used by several objects, I keep it in a macro and use RETURNED_PARAMETERS to get the data back to the calling object.