When trying to create a User Function in CFX-Pre, the Argument Units widget appears to be disabled and I can't type anything into it. The Result Units widget works fine.
This is a minor bug in the CFX-Pre GUI initialization file.
You can edit the file 'CFXPreGui.ccl' in your CFX installation (located in the /etc directory). Simply change the following section:
PARAMETER GUI: Argument Units
Type = String
Editable = True
Extension = False
Picking = False
So that the 'Editable' tag is 'True'.