Dean:
1. Create a new parameter for this part, give it the variable "bha" (so it matches the D Ellipse Arch Opening parameter, which may help for scheduling and parameter transfer) and the name "Bottom Height of Arch".
2. At the beginning of the Master Script, add the line:
gs_arc_h=B-bha
This will calculate the gs_arc_h variable (named Arc Height) as the difference between the height of the door and the Bottom Height of Arch.
3. After the !!CURVED TOP CALCULATION!! line in the Master Script are some formulas for correcting the arch height based on the width and height of the door so it does not exceed these variables and create an impossible situation. You can work through these if you are concerned about the users entering a wrong Bottom Height of Arch parameter.
4. Since this work is done in the Master Script, the correct values are passed on to the 2D and 3D Scripts, so you should not need to fool with these scripts.
5. Click on the "X" next to the "Arc Height" parameter to hide it in the part's dialog box.
HTH
David