How to restrict choices in Table References

I want to select a value from a table to use in another table, but only want to select from certain records.

Example

Table 1 has four fields

- Title

- P1

- P2

- Subject (To be filled from Table 2)

Table 2 has three fields

- Subject

- P1

- P2

Note that P1 and P2 are pulled from other tables.

Table 2 has a long list of records but only certain records are relevant so I want to restrict the selection.

The restriction is to be based on the value of P1 and P2 in table 1. So if I create a new record and select values for P1 and P2 I want the database to find the corresponding records that have the same values of P1 and P2 in Table 2 and display these records for making the choice for the "Subject" field in Table 1

I'm looking for suggestions on how to approach the problem.

Thanks.