I have now noticed a second error in my posting - the undefined Symbol is actually "LOOK2". (NOT LOOKUP2). I really need less coffee, I think.
I did a search of my code, and Darrel's code, and there is no LOOK2.
I removed the include for Darrel's code and the problem goes away; however if I add a statement containing "LOOKUP2", even if it's not executed, the error returns, so it's a library problem, and not a coding problem, It seems that somewhere in the compile process, "LOOKUP2" gets changed to "LOOK2" and bombs.
The search continues...