I think you need to add also the tables from which you are taking the fields from so for example
in_mstr.in_qty_avail - in.mstr_in_qty_all and so on.
Here is an example of an equation I made for filtering Purchase order acknowledgment messages:
((edmfs_mstr.edmfs_doc_in = False) and (edmfs_mstr.edmfs_domain = global_domain) and (edmfs_mstr.edmfs_mfd_name = "MFGOrderAck"))
Hope this helps,