[Groff] blm blues

[Miklos Somogyi]

I am trying to produce a macro for request blm that would set space as  
a given fraction of the current vertical spacing.

I did the following:

-------------------------------------------

 .de blank
.       nr blankreg (c;\\$1)                                  this  
would accept things like ".blank 0.42" and convert to "u"
..

.de blank_aux
.      sp (\\n[.v]u*\\n[blankreg]u/28340)u        this macro  would  
generate space when .blm finds a blank line
..

.blm blank_aux                                                this  
nominates blank_aux to be called by .blm

--------------------------------------------

This does not work (does not produce any space). The registers seem to  
produce the right answers and if I use them
without defining .blm, I get the spaces.
Also, the .blm thing works ok if .blank_aux does not have a reference  
to \n[.v].
What is wrong here?
Plse help!

Miklos