Block move problem in lisp

I want to move a block using lisp where it moves back and forth only on a
specified angle. The sequence would go something like this; the block
would be picked, then a predefined first point is selected, then I want my
users to be able to see the block sliding back and forth <animated> along an
angle that was previoulsy defined in the routine. The user will have a
choice of either hitting enter, or right clicking, or clicking a point along
the angle or typing in a distance. By hitting enter, or right clicking, the
second displacement point of the move will default to the same point as the
first point of the move. I tried this, with ortho on, (command "move" Block
"" BlockInsertionPoint (if (= (getpoint) nil) BlockInsertionPoint)) and it
didn't work, but you may get the idea. I never got far enough to figure out
the sliding back and forth along a certain angle. I was going to try some
setting the "baseang" variable to do that, but dunno if it will work. As
for now, I just wanna get the block to move right.

 

Yeah, grread was suggested by another person, but it is way over my head.
He explain that the move would have to be in some sort of a loop. Don't
supposed you could explain it in normal english?

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