When playing with the area blocks in the data.mp file I found def a_blocks_SKBB_ (expr p,o,s_beg,s_end,d_beg,d_end) = Different from def a_blocks_SKBB (expr p) = The name has an _ on the end, however, I have no idea how to use it, also if I copy it in to a code endcode layout I cannot get it to work even if I make it def a_blocks_SKBB_TEST (expr p,o,s_beg,s_end,d_beg,d_end) = It seems to go into an infinate loop, is this maybe as I have not defined the extra variable o,s_beg,s_end,d_beg,d_end, if that is what they are, and if so how do I define them. Basically it looks interesting, but I have no idea how to play with it, Help! thanks Andrew