Like #ifdef ... #endif in C/C++ and include_once("includefilename") in PHP
it would be nice if mathcad provided for a conditional reference to another worksheet so
it would not be possible to reference a worksheet more than once.
For example if worksheet "a.xmcd" references worksheet "b.xmcd" and worksheet "b.xmcd" references "a.xmcd"
this causes an infinite loop and eventually causes mathcad to crash.
Dr. Milt Benjamin