To apply the filter when the page loads, set the default value in the filter properties to the GUID (converted to a string) of the desired object.
In this case, save the GUID (converted to a string) of the desired OrderCreator, pass it to the datagrid2 via a page parameter or a data view, and set the default value accordingly.
I had a similar issue recently and what helped me was the Set_Filter javascript action that comes with the DataWidgets module. There you can just enter the name of the filter and add the value that should be set. in this case just let the datagrid retrieve all the objects and then set the dropdown filter to the desired value (guid of the user as a string)