Entering responsibilities with the value blank or space

[Soady, Phil]

Hi WUggers,
is there a trick in PFAC to entering responsibility rule nominating that

1 of n elements from the container should be tested 
for exactly and only for the value <BLANK>.

Leaving the value empty seems to imply the no check.  YELLOW light
incomplete rule.

SO how does one force feed the rule with <blank> / Initial value.
Does this imply I a writing a function and building my own customizing ?


regards
Phil