Label, forward reference and opattr

[jj2007]

I am aware of this thread, but it didn't solve my problem:

Code Select Expand

codesize macro algo
  print "size="
  mov eax, offset &algo&_END-&algo&
  print str$(eax), 13, 10
ENDM
...
MyAlgo proc
  ret
MyAlgo endp
MyAlgo_END:

That works. However, I would like to check whether MyAlgo_END exists, and there I am in trouble:
- ifndef fails:
         tmp$ CATSTR <algo>, <_END>
         ifdef tmp$
.. and various other constructs like &algo&_END etc return either always "defined" or always "undefined".
- opattr fails for MyAlgo_END because it is a forward reference
Now my question:
opattr works for MyAlgo because MyAlgo is a proc and defined via PROTO. Is there a similar way to pre-define the label?
Thanks for any hint.

EDIT: I found the solution (in an old code of mine ::))

Externdef MyAlgo_END:NEAR