What Joey said. For every pointer used in a given function, insert the following line at the beginning of the function. If there aren't any pointers used, then you don't need anything at all:
Code:
while(![pointer name]) { wait(1); }
Change the [pointer name] to the appropriate name minus the brackets (player, camera, etc}. When the pointer is no longer null, the function will execute. Another way is "while([pointer name] != null) { wait(1); }" but I think the way I posted above is "faster."
It's perfectly all right to check for more than one, too. I have functions that use more than pointer, and I check for all of them. Just do this:
Code:
while(![pointer name1] || ![pointer name2]) || ![pointer name3]) { wait(1); }