Create Procedure NoNeedForAnSP @myValue int
 as
select TableP.*, tableX.FK, tableX.sales
 from tableP inner join
 (select * from tableA
  union
  select * from tableB
  union
  select * from tableC
  union
  select * from tableD) tableX
on tableP.PK = tableX.FK
where tableP.PK = @myValue

Brilliant Cetin!! Thank you very much.
Now a followup question (before I give you stars). Your solution works, but at what cost? Does this solution select all the records from TableA, TableB, TableC and TableD and place them into a temporary table TableX?

Thanks,
Einar