Not sure if I understand your problem correctly and I'm not sure if this is any different than what you are doing, but the following code ought to do it. You can replace ACC.0 with whatever bit you would like to test.

MOV R0,#40h ;Replace with first memory location
LOOP:
MOV A,@R0
JB ACC.0,BITSET
INC R0
CJNE R0,#50h,LOOP

NOBITSET:
;if you get here, not bit 0 of the
;regs were set
BITSET:
;if you get here then at least one bit 0 of
;the regs were set