How do you check parallelism of a surface to a plane using the AP command in WinCmes. We are using Windows 95 and WinCmes ver 3.3 on a G80-C.
The following code is what was used:

UG,100,48\AX-,4,48\AP,4,P,Z,P/P\.002

The following error message come up:

Cannot create a unique plane through given points!

Would appreciated your input.