The clue is the common denominator for lines 12, 13 and 17... it doesn't like your variable.

I don't have PICBasic, only PICBasic Pro, however, whilst your code would be valid in PBP, in PBC I believe the variables are predefined... you must use them, although (and I stand to be corrected) you might be able to alias them... try this as a starter...

for B0 = 1 to 4
high 0
pause 1000
low 0
next B0

Consult the PBC manual for variables.