SQL Transaction Statement

Hi,
Im trying to get my headaround the sqltransaction class.

I can do the simple statement like (see below).
//Execute Stage 1
SqlTransaction trans;
 using (trans = con.BeginTransaction())
            {
                try
                {
string strInsertData = " INSERT INTO BLAH BLAH BLAH WHERE BLAH =@BLAH";
                    SqlCommand cmd_ExecuteInsert = new SqlCommand();
// MORE CODE
 cmd_ExecuteInsert_RMA.Transaction = trans;
trans.Commit();
}
catch
{
 trans.Rollback();
}

//Execute Stage 2
// OK now I want to  Update another database, but if it fails I need to Roll back stage 1
// Can someone provide an example on how to do this please