Question about how include a new rule in wmake
 

Hello,
i am trying to include #include <mpi.h> library in a solver to be able to use the basic functions of MPI. When I compile the solver named
"simpleFoam_MPI" with wmake the compile line generated is:

>$ g++ -m64 -Dlinux64 -DWM_ARCH_OPTION=64 -DWM_DP -DWM_LABEL_SIZE=32 -Wall -Wextra -Wold-style-cast -Wnon-virtual-dtor -Wno-unused-parameter -Wno-invalid-offsetof -O3 -DNoRepository -ftemplate-depth-100 -I/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/src/TurbulenceModels/turbulenceModels/lnInclude -I/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/src/TurbulenceModels/incompressible/lnInclude -I/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/src/transportModels -I/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/src/transportModels/incompressible/singlePhaseTransportModel -I/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/src/finiteVolume/lnInclude -I/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/src/meshTools/lnInclude -I/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/src/fvOptions/lnInclude -I/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/src/sampling/lnInclude -IlnInclude -I. -I/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/src/OpenFOAM/lnInclude -I/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/src/OSspecific/POSIX/lnInclude -fPIC -Xlinker --add-needed -Xlinker --no-as-needed Make/linux64GccDPInt32Opt/simpleFoam_MPI.o -L/users/rechimal/OpenFOAM/OpenFOAM-3.0.1/platforms/linux64GccDPInt32Opt/lib \
-lturbulenceModels -lincompressibleTurbulenceModels -lincompressibleTransportModels -lfiniteVolume -lmeshTools -lfvOptions -lsampling -lOpenFOAM -ldl \
-lm -o /users/rechimal/OpenFOAM/rechimal-3.0.1/platforms/linux64GccDPInt32Opt/bin/simpleFoam_MPI

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I would like to change de g++ compiler by mpic++ compiler changing some rule in the wmake tool. I was trying to find which is the rule but I could not find any. How can I do this using wmake (it works if I just copy the line and I change it by hand, but I would like to understand a little bit how wmake works).

Thank you in advance.