1)is it possible to share a global static varaible in the ISR and the main function?

2)i tried it alot and the compiler keeps telling about some data overflow.

2) The overflow is "too many variables", not their use, move some from DATA to IDATA or XDATA.

1)
yes and no
if the variable is "common" e.g. a pointer incremented in the ISR and read and decremented in the main - yes
if the variable is "shared" and has different purposes in main and the ISR - no.

Beware
for common (see above) variables more than one byte long you MUST disble the assiciated interrupt(s) while using it in main.

Erik