How I can change custom build "Object file" value

[amarty]

 Hello!

File properties, "Advanced" tab, field "Object file" disabled and alwais contain "my_file.h.gch". I think this name is used to check that my_file.h need to be rebuilt? How I can place "moc_my_file.cpp" instead of "my_file.h.gch" into that filed? I try to edit .cbp project file manualy, but I don't know what tag or attribute must be used.
Anybody have solution?