CRM and Sharepoint integration question

In CRM, each account has a rank code.  In Sharepoint, there is some documentation say for rank code 1, 2, 3 but not for rank code 4.

I have CRM account with rank code 4.  THe design is:

On the CRM form, have a button that can be enabled or disabled.

It is enabled when Sharepoint documentation exists.

So basically, Sharepoint and CRM will have to talk.

If I always enable the button, the end user wastes a click to go to the empty Sharepoint library page with "No documentation found".  So I'd like to see if I can determine whether documentation exists on Sharepoint 2010.

How can I make this happen?  Thank you in advance.