Aavlaibility check for material and Substitution material

Hi Gurus,

I have a requirement where in I need to check the availability of a material and if there is not availability then I need to find out the substituted material maintained for the material.

for example, Material M1 has no stock in ECC and Material M2 is maintained as substitution in the SCM system. I need to figure out the tables or any Function module that can fetch the Material M2 if I provide Material M1.

I am able to check the material availability using the BAPI "BAPI_AVAILABILITY_CHECK". But I didnt find any FM or way to find the substituted material for a material.

Please help me out.

Thanks.

Anand.