[galaxy-dev] Path to tool designation in tool config xml

Hi, I'm trying the add tool tutorial at http://wiki.g2.bx.psu.edu/Admin/Tools/Add%20Tool%20Tutorial . It works, but how do I designate the path of the tool if it's not dropped into the same directory as the tool config xml? Some executable may not be in the directory. Surely it couldn't possiblely be the case with external tools like BLAST, isn't it?! But looking at the BLAST config xmls I couldn't make out the difference and I didn't find any documentation on how to designate the path of the tool. Help appreciated, thank you. Timothy