> Is it possible to define two nybble variables for the same 8 bit
> register. I am using a 16F84A

Hi, I don't think so. It's the kind of thing that would useful when
addressing port nybbles, and I don't recall ever seeing that. But
maybe I was away that day and there is another, simpler, way.
What's below could be completely OTT

Perhaps break it down into macros. That way you'd need to do the
hard work just the once. (And the macro defines both the variable
and what you want to do to it)

Have 3 variables altogether. dg1, dg2 (that hold the numbers as the
low nybbles) and dg3, (which is a composite, if necessary)

For example, increment the high nybble

i_upper  macro       ;increment upper nybble of dg3

         incf    dg1       ;inc the number which forms the upper nybble of
dg3

;***** your limit test here *****  to keep number within bounds

         movlw   b'00001111'    ;clear upper nybble
         andwf   dg1

         swapf   dg1,w        ;make it the high nybble in W
         addwf   dg2,w        ;add to what will be the low nybble of dg3
         movwf   dg3          ;make new value for dg3

         endm

Similarly for d_upper, i_lower, and d_lower. You may be able to
shave a cycle or two from the macros by trying different instructions

Now when you want to eg increment the number in the lower nybble,
you'd simply type

        i_lower

and dg3's lower nybble will increment within your limits

Hope that helps

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