Alt. Solution to Incorrectly Applied Target-Specific Variable

[Sean Smith]

Initially, I attempted to use a target-specific variable in the 
following way (simplified example):

LowLevelFunc = LowLevelFunc1.o

a.out : Main1.o MidLevelFunc.o LowLevelFunc1.o
   ${CC} $? ${LowLevelFunc} ${LIB} -o $@

alt_a.out : LowLevelFunc = LowLevelFunc2.o
alt_a.out : Main2.o MidLevelFunc.o LowLevelFunc2.o
   ${CC} $? ${LowLevelFunc} ${LIB} -o $@

Main1.o : MidLevelFunc.o
Main2.o : MidLevelFunc.o

MidLevelFunc.o : ${LowLevelFunc}

LowLevelFunc1.o :
LowLevelFunc2.o :

Ignoring my mistake, you can see the point is this - depending on a 
different driver program, it should use a different lower-level function 
to plug into the mid-level function. I have since learned that 
target-specific variables only work in the command lines, and not as 
part of prerequisites. Looking in the help-make archive, the two 
suggestions I came across were to redirect to another rule or to use the 
eval function. I was unable to understand how to make either of these 
work for my situation. Any suggestions?
The actual situation has more files and is slightly more complicated by 
fortran modules and handling both the .o and .mod files.

Thanks,
Sean Smith