Server.Transfer And Passing Values

When using the Response.Redirect in test1.asp in this manner:

Response.Redirect ("test2.asp?err=something&msg=somethingelse")

You can pass values calculated in test1.asp to test2.asp.
But this is a round trip redirect - and also shows passed values in
the address bar.

But when using Server.Transfer, as in:

Server.Transfer ("test2.asp?err=something&msg=somethingelse")

This is apparently not allowed, as I get an error claiming that
non-relative references in the path of the file are not allowed.

My question is:

*Without* using application or session stores, how can you pass values
between pages called in this manner - values that are not a part of
the originally submitted information?