Blank Purchase Order

Hello Community

I am looking for some information or a document in setting up Blanket Purchase Order (BPO) for services offered by a service provider/vendor.

For an annual contract a BPO will be raised and will be released as per monthly schedule.

As provider may offer many services under one roof , is it possible to generate PO from BPO for the sub-services offered?

For example -

For example, if  'HOUSEKEEPING SERVICE' is the service offered by a service provider/Vendor - ABC.

While the sub-services offered under this service are a) To clean up the lobby b) Trimming trees  c) Disposing Dry Garbage