autolisp and subtract command

[oakam]

I am trying to write a autolisp function which select a 3d object and then select another and subtract from the first. I work fine for one object but if I tried to subract more it doesn't work. Points read from en file. When I use the data of the file manually everything goes fine but not when use the function (not found). Is there is antyway to do it?
the function do the following

read points from the file to draw boxes which some of them to be subracted from the other. Only the first subtraction successed.

thanks

[csiarch]

I don't know anything about writing autolisp code but from your description it sounds as if you need to include an option in the code where you can "branch off" to select more than one entity.

Mnenomically speaking....

the routine would prompt for the first object,

then prompt you to select another object to be subtracted....(you got this far)....

THEN, the program should ask if you wish to subtract another object....

If YES, then prompt to pick a new object (while remembering the last two objects picked). [Subtract the third object from the previous two]. Then the program sould loop back to the start of "If YES" and ask if you wish to continue.... and so on, and so on.....

If NO, then End.

Sounds like an issue of working out the program logic. A program should be able to be made to respond as generally described above, regardless of the programming language being used.

Hope this helps some....