How to wait until a callback function has completed

Processing Beginners
4

OK I have managed it.
It turns out that if I put
while(loadCompleat == false) { }
It would not work but if I put something in that wait function it would. Like this:-
while(loadCompleat == false) {delay(10); }

I started out printing the loadCompleat variable and that worked but made a mess of the console so changed it to a delay call.