Simple Function Problem, please help

[mpd]

def columncheck(c):
   x=5
   pos=False
   while not pos:
       if dboard[x][(4*c)-1]== " ":
           pos=True
       else:
           x-=1
   return x

My brain is fried... I tweaked the function to make it a little clearer, but if there's an obvious reason for it not working, I don't see it.  What's dboard?  How is it defined/iniitialized and set?