[ic] How do I remove the null byte separating [cgi . . .] entries

[interchange-users@interchange.redhat.com (Balster)]

HELP, I'm having a NULL byte problem.

I have a form with several checkboxes all with name=b

the receiving form has something like:
[loop list="[cgi b]"]
  [value name=b set="[loop-code]" hide=1]
  [include use_value_b.txt]
[/loop]

The first [value b] has the value of the first checkbox
Each remaining [value b] has a NULL byte followed by the value of the 
checkbox.

I have heard that I could use a nullselect filter for this, but I've 
searched thru all of the docs plus over 50 Megs of interchange-user 
archives looking for a syntax example.  The only mention in the docs of a 
nullselect filter is for a type=combo.  The only examples I can find in the 
sample store are to set up a filter for a specific database file in the 
mv_metadata.asc file, but I'm having the problem with the [cgi] tag, not 
with a database file and it does not appear that mv_metadata.asc applies to 
this tag.  Does anyone know how a nullselect filter can be applied to a 
[cgi] tag???