SQL Server 2005 - 授予创建存储过程的权限（但没有其他对象）

I want to grant a user permission to create, alter, and execute stored procedures, but without the ability to create other database objects. I excluded them from the role db_ddladmin, but explicitly granted the permissions "Create procedure" and "Execute". These permssions appear in the effective permissions list. However, when I try to create a stored procedure with this login, I get the following error: I want to grant a user permission to create, al