User-Defined Func Syntax For Table Return

Hi all!

I'm trying to use a UDF that returns a table, but I'm not sure of the syntax to invoke it. I've found examples in BOL and on-line like the following:

SELECT * FROM dbo.fn_MyTableFunc( 123.09, 'MyID' )

But I need the input parameter to be obtained from another table. For a very simplistic example, I've got 4 tables (and yes, I know that I can get the results I want for this example without using a UDF, but humor me):

CREATE TABLE tUser (UserID int PRIMARY KEY, UserName varchar(50))
CREATE TABLE tAcctGroup (AcctGroupID int PRIMARY KEY, AcctGroupName varchar(50))
CREATE TABLE tAcct (AcctID int PRIMARY KEY, AcctGroupID int, AcctName varchar(50))
CREATE TABLE tMapUserToGroup (UserID int, AcctGroupID int)
GO

INSERT INTO tUser VALUES (111, 'Me')

INSERT INTO tAcctGroup VALUES (1, 'NY')
INSERT INTO tAcct VALUES (11, 1, 'New York City')
INSERT INTO tAcct VALUES (12, 1, 'Syracuse')

INSERT INTO tAcctGroup VALUES (2, 'GA')
INSERT INTO tAcct VALUES (21, 2, 'Atlanta')
INSERT INTO tAcct VALUES (22, 2, 'Savannah')
INSERT INTO tAcct VALUES (23, 2, 'Augusta')

INSERT INTO tAcctGroup VALUES (3, 'TX')
INSERT INTO tAcct VALUES (31, 3, 'Dallas')
INSERT INTO tAcct VALUES (32, 3, 'Houston')
INSERT INTO tAcct VALUES (33, 3, 'El Paso')
INSERT INTO tAcct VALUES (34, 3, 'San Antonio')

INSERT INTO tAcctGroup VALUES (4, 'CA')
INSERT INTO tAcct VALUES (41, 4, 'Los Angeles')
INSERT INTO tAcct VALUES (42, 4, 'San Francisco')

INSERT INTO tMapUserToGroup VALUES (111,2)
INSERT INTO tMapUserToGroup VALUES (111,4)
GO

CREATE FUNCTION dbo.ufnGetAcctList(@AcctGroupID int) RETURNS @tAcct table (AcctID int, AcctName varchar(50))
AS
BEGIN
INSERT INTO @tAcct
SELECT AcctID, AcctName FROM tAcct WHERE AcctGroupID = @AcctGroupID
RETURN
END
GO

I know that I can do:
SELECT * FROM TestDB.dbo.ufnGetAcctList(4)

But I want the equivalent of:
SELECT AcctID, AcctName FROM tAcct
WHERE AcctGroupID IN (SELECT AcctGroupID FROM tMapUserToGroup WHERE UserID = 111)

Which uses tMapUserToGroup to obtain the AcctGroupID to pass into the function. The results would be:
AcctID AcctName
-----------------------------
21 Atlanta
22 Savannah
23 Augusta
41 Los Angeles
42 San Francisco

Any thoughts?
Thanks in advance for your help.
Cat