Thanks guys for the additional input. I'm running 2.60 and MPLAB 8.87 which has never been a problem.

I've come across a previous bit of code that used the highbyte / lowbyte and that compiled fine so it must be to do with something in that statement. I'll try changing the variables (removing the underscore) and see if that has any affect, but as the example code I found also used underscores than I can't see that being the issue.

Malcolm