You are specifying the path to a material library:
C:\ProgramData\SolidWorks\SolidWorks 2013\Custom Materials\solidworks materials.sldmat
Firstly, does that file exist in that folder? solidworks materials.sldmat is a standard library of materials and usually lives in C:\Program FIles\SolidWorks Corp\SolidWorks\lang\English
Secondly, solidworks materials.sldmat does not contain a Mild Steel Grade EN10025-S275
Could it be a Custom Material? If so, put the correct path to that custom material library into the SetMaterialPropertyName2 line
Excuse my ignorance but why would you need to create a macro to add a material to the material 'favorites' list? If you simply edit the material to bring up the material list menu, you can select the 'Favorites' tab on the right. Assuming you have created a custom material, you can select it from the list on the left and choose the 'Add' button to include it to you favorites menu.