Please help constrain moviclip movement

Hi I wrote before and got good help telling me how to constrain my movieclip when it is made to load in a random position. However I have now changed the position that it is allowed in. I am useless at maths and i hope someone would be nice enough to help.

It is a battleships game. I only want the alpha 0 moviclip ( myclip- off the stage to the right). to be allowed to appear in the area covered by the red square movie clips

I can’t attach the fla so you can see the fla on my website.( scroll down to see).my website

i would be really grateful for any help.
lesley