One way I did this was to drive the changes from a drawing.
what happens here is that the error message gets written into across the
drawing, flagging the users data entry error by writing it across the
drawing.
Here's a snippet from a pro/programs section of an assembly:
T=(4/3)*(P0:8*COEF_FRIC*FS)*(((OD:4)^3-(ID:4)^3)/((OD:4)^2-(ID:4)^2))
ERROR_FLAG="
IF ID:4>=OD:4
ERROR_FLAG ="ERROR IN SPECS. ID IS >= OD FOR FIBER."
TORQUE = "???"
ENDIF
Note that I could (should ?!) have initialized the ERROR_FLAG outside if the
IF statement.
You just need to add a line that sets the error flag condition to the value
you desire _after_ you check the IF statement.
Other than that, it is straight forward. Just create a note in the drawing
that displays your error message.
This won't create a pop up window, but will allow you to catch the error.
That is one way to do it. I am sure there are more efficient ways to get
similar results. This could also be done using the VB API, or JLINK, etc.
Hope that gives you some ideas.
-tsl
todd@coldfire-e.com