Parameter Query For Unmatched Records

I have to build a query and I am not sure how to build it.

Our data has providers with different products. We have an “DGH” product and a “PRM”. I need to find the provider that don’t have both. Its sounds very simple, but I am having an awful time figuring it out. Sometimes I get a record that has both products, it is probably how my where clause is working.

Anyway, here is an example of what I don’t want in my records because this is good. It has a DGH and PRM.

pro_pcs pro_lname pro_fname prop_prd pro_tax1 pro_addr100018791 Smith John DGH 12345868 Kiem ST
00018791 Smith John PRM 12345868 Keim ST

I would want to see this one because there only a DGH and it need to have a PRM product.

pro_pcspro_lname pro_fname prop_prd pro_tax1 pro_addr1
00018791 Rubin SamDGH2345868 Kiem ST

I came up with this below and it seems to be working. The only thing is, I now have to make this so people can add a parameter on the pro_tax1 to see the different records. Is there a better way to do this or how can I use what I have below and add a parameter too it.

Select pro_pcs, pro_lname, pro_fname, pro_addr1
from #ALLProducts
Where pro_tax1 = '12345868'
and prop_prd = 'DGH'

except

Select pro_pcs, pro_lname, pro_fname, pro_addr1
from #ALLProducts
Where pro_tax1 = '12345868'and prop_prd = 'PRM'