COUNT ( FROM Nested SELECT)

 HI All,
 
I have what is most likely a simple MS SQL query problem (2005).
I need to add two computed columns to a result set, both of those columns are required to provide the count of a query that contains a parmamter. (The id of a row in the result set)

 
3 Tables (Showing only the keys)

t_Sessions
-> SessionID (Unique)
 
t_SessionActivity
-> SessionID (*)
-> ErrorID (Unique)
 
t_SessionErrors
-> ErrorID (1)

 
I need to return something like (Be warned the following is garbage, hopefully you can decifer my ramblings and suggest how this can actualy be done)

SELECT SessionID,
    (SELECT COUNT(1) AS "Activities" FROM t_SessionActivity WHERE t_SessionActivity.SessionID = t_Sessions.SessionID),
    (SELECT COUNT(1) AS "Errors" FROM  dbo.t_Sessions INNER JOIN
                      dbo.t_SessionActivity ON dbo.t_Sessions.SessionID = dbo.t_SessionActivity.SessionID INNER JOIN
                      dbo.t_SessionErrors ON dbo.t_SessionActivity.ErrorID = dbo.t_SessionErrors.ErrorID WHERE  t_SessionActivity.SessionID = t_Sessions.SessionID)
FROM t_Sessions
 
Any help greatfully received.
 
Thanks