"Proteus simulator and not the actual LCD. After testing on simulator I will be testing it on actual LCD. "

I don't think that is a right approach. When it comes to time-critical events ( and LCD control is one such ) simulators fare very badly. On the other hand an In Circuit Emulator ( ICE )can do the job quite well.

SO don't try to validate such time critical code on simulators. I am afraid you will have to build the actual hardware for testing in the absence of an ICE.

Raghu