PIC24FJ - LIN Bus transmission
It sounds like the real solution is at a higher level of protocol.  At a higher level, you should know when it's OK to send and when it's not.

I'm not familiar with LIN in particular, but there is probably a means of addressing this issue already defined as part of LIN.  One possibility is that nodes send when they feel like, and the resulting collisions are detected and dealt with in a orderly manner.  This is how CAN works, for example.  Or, there is higher level logic to guarantee only one node at a time is supposed to transmit.  Most RS-485 bus implementations work that way, for example.  The Dallas one-wire bus works that way too.

Implement whatever mechanism that has already been decided upon.