regarding assembling branch instruction

[Sivaprasad.pv]

Hi all,

Initially our  custom processor support only one  unconditional branch 
instruction  'bra' of 20 bit range (32 bit instruction).
Now we are planned to add 16 bit unconditional branch instruction 'bra' 
of 8 bit range.
both shares same instruction name 'bra'.But it leading a problem for us.
For example:

bra Label
nop
nop
...
Label: nop

In first pass 'Label'  address is treated as 0 so it is selecting 16 bit 
instruction.
In second pass it finds that the 'Label' is out of 8 bit range and fails 
to generate appropriate 32bit instruction opcode.

please help me inorder to resolve this issue.

Thanks,
Siva Prasad.