Henrik was right there, I was selling PBP short.
It shouldn't matter with PBP programs under 2K anyway,
but you'll appreciate the practice if you use another language.

You remember the old interpreted BASIC with line numbers?
Code:
10 CLRSCREEN
20 PRINT "HELLO WORLD"
30 GOTO 20
It's the goto in that one that searches a list to find the line/label it's after.
In this case (30 GOTO 20), it searches from the beginning, but if the destination
line is after the GOTO command, it searches from the GOTO command onward.
Some interpreted Pic BASIC language (not PBP) probably does the same thing
even if you don't need to use the line numbers anymore.

If you just want to check a byte variable is in BANK0 to access it without switching,
you can increment it with inline assembler.
Code:
@ incf _B1;
should be the same as
Code:
B1 = B1 + 1;
If byte B1 was not in BANK0, a different variable or some unassigned RAM will be incremented.