Dear,
If you want to consider the In house production time then you need to have MRP planning parameter as
Scheduling = 2 Lead Time Scheduling and Capacity Planning.
If you want to exclude group of materials from MRP run then use exit M61X0001 FM EXIT_SAPMM61X_001 for MRP Run in MD01 for particular material group.
Refer below link for more info.
http://scn.sap.com/message/6627414#6627414
Regards,
R.Brahmankar