Restriction of Service materials to an Opportunity

Hi SAP Gurús,

I've a requirement in which I need to restrict a group of 5 Materials, to a certain Tx Types (Opportunities & Leads). I already created my materials, as a Service Material in COMMPR01 Tx, set the Item category Group as SRVP, I chose a Unit of measure, description, and also chose a Category for my New Material previously created under the Standard Hierarchy R3PRODSTYP.

Then, I made the Item Category Determination, where I chose my Tx Type and the item Category belonging to my Tx Type.

When I attempt to reference my materials using the match code, the system shows me the total of material existing in the system independently of category, item category or item category group.

Any approach it's really appreciated.

Thanks in advance,