Aggregate Bitwise OR On A Column

I am trying to get a culmulative Bitwise OR operation on a column by query - rather than using a CLR function.

The problem is shown below:

CREATE TABLE #Operations (
PK INT NOT NULL IDENTITY(1,1),
UserName VARCHAR(50) NOT NULL,
UserProcess VARCHAR(50) NOT NULL,
ServerOperation VARCHAR(50) NOT NULL,
Permission INT NOT NULL );

[Code] ....

So Far I've tried SUM - wrong results, and STUFF - which doesn't seem appropriate for bitwise operation - neither give useful results.

-- SUM Operation - fails
SELECT DISTINCT
UserName,
ServerOperation,
SUM(Permission) AS Permission
FROM #Operations

[Code] ....

It may be possible to materialise the permissions each time one is changed (e.g. by to use a cursor ), however I would prefer a query or function or combination to generate the result.