Combine Multiple Sql Calls Into 1

I have an old app that I'm trying to recode and improve performance.

From the start it makes three seperate calls to a db, checks to see if the record exists, if it doesn't it adds it, then takes the data from all three and inserts it into a final call.

Here is a quick example of the script

Select * from table1 where id = " & tempVariable
If Not RS.EOF Then
strTable1 = RS("SomeRec")
Else
RS.ADDNEW
RS("SomeRec") = tempRec1
RS.UPDATE
RS.Requery
strTable1 = RS("SomeRec")
End If
RS.CLOSE

Select * from table2 where id =2
If Not RS.EOF Then
strTable2 = RS("SomeRec")
Else
RS.ADDNEW
RS("SomeRec") = tempRec2
RS.UPDATE
RS.Requery
strTable2 = RS("SomeRec")
End If
RS.CLOSE

Select * from table3 where id =3
If Not RS.EOF Then
strTable3 = RS("SomeRec")
Else
RS.ADDNEW
RS("SomeRec") = tempRec3
RS.UPDATE
RS.Requery
strTable3 = RS("SomeRec")
End If
RS.CLOSE

INSERT INTO Table4 (Table1, Table2, Table3) VALUES ('" & strTable1 & "', '" & strTable2 & "', '" & strTable3 & "'


These is probably an easy solution however I don't know where to start. Any help or ideas will be greatly appreciated.
Thanks
-Scott