& bthexinblz()
 
  Syntax: bthexinblz(<MapOBJ>,<x>,<y>)
 
  The function determines if the hex designated by <x>,<y> on <MapOBJ> 
  is within a blocked landingzone
 
  The function returns 1 if the hex is blocked, and 0 otherwise.
 
  Error Messages:
 
  * If <MapObj> is not valid the function returns #-1 INVALID MAP
  * If <x> or <y> are outside the boundaries of the map the function 
    returns #-1 INVALID COORDS 
 
  Example:
  Given that #62 is a valid MapObj and that hex 10,11 IS within a 
  blocked landingzone:
 
  >think bthexinblz(#62,10,11)
  1