how do you determine which direction cells will move toward membrane?
Since this is not my area of expertise, I searched Google under the key words "'cell movement' membrane" to get these possible sources:
http://www.sci-journal.org/index.php?template_type=report&id=56&htm=reports/a11/index.htm&link=reports/home.php&c_check=1
http://www.jem.org/cgi/content/abstract/140/5/1207
http://www.uta.edu/biology/wilk/classnotes/cellphys/Cell%20movement.pdf
(Broken Link Removed)
http://links.jstor.org/sici?sici=0033-5770(198509)60%3A3%3C341%3ABMACMC%3E2.0.CO%3B2-B
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search.
I hope this helps. Thanks for asking.