DEFINEs cannot be changed at run-time. These are used by the compiler at compile time
only.

WDTPS options are set in the PIC configuration register. These you can change at run-time
on some 18F parts.

This thread shows two examples;
http://www.picbasic.co.uk/forum/show...ghlight=config

Just bear in mind that changing some configuration settings at run-time may result in major
problems - so be careful.