If you wanted to avoid usiing extended stored prcedures you could do it like this. It's a bit more understandable than multiple nested select statements that are required for xp_execresultset to work properly...

-- Specify the user account which should be

DECLARE @login VARCHAR(50)

SET @login = 'my_user_id'

DECLARE @sql VARCHAR(max)

Select

      @sql = Coalesce(@sql, '') + 'GRANT EXEC ON [' + [name] + '] TO [' + @login + ']' + Char(13)

FROM sysobjects WHERE xtype = 'P' AND [name] NOT LIKE 'dt_%'

EXEC (@sql)