Building a List of Coordinates to Feed to the Trim Command

As luck would have it my algorithim I built last week which works very good to draw lines between objects hit a snag when suddenly the objects were changed to a new shape. What I need to end up with is a line drawn between two points and then to trim this line very carefully along a set of picked points. This can be done fairly easily by hand, doing it with LISP is proving a bit of a task, and it still may be impossible to do.

My thinking is to do a while or repeat loop to build a list of coordinates. Then feed that list of coordinates to the trim command. My first attempt to just build the list of coordinates is proving difficult, again most likely due to my lack of experience with building lists.

(setq z 0)
(while z < count
 (strcat tl " " (polar (polar pt1 (dtr 0.0) (* 4 count)) (dtr 90.0) 3))
)

I was hoping to end up with a list of coordinates which stayed horizontal but increased in distance from pt1 by 4 each time through the loop. So that tl would end up something like

(0.0 3.0) (4.0 3.0) (8.0 3.0) (12.0 3.0).....etc

I was then wishing to feed this list to the trim command something like this:

(command "._trim" (a_rectangle_to_grab_the_boundary_shapes) tl "")

The number of boundary shapes (count) changes with each use of the code but they are equally distributed along the horizontal so I'm thinking some kind of sequence could be done. And again this is for a totally automated process so no user input allowed.

UPDATE: I got it resolved. As I look at the code I follow it well, and watching it work I follow it, but when it's all done and the lines are trimmed precisely through the webs of all the channels, no matter how many of them and no matter what the o.c. spacing is, I can only look in amazement. This stuff really can save a lot of time for designers. And yes, it was a mathematical layout which allowed for a mathematical solution.