How to use item references in Interactive Grid for dynamic values

I have an IG and for some column properties (e.g. Heading, Help) I refer to item values like "&P10_MyItemValue1.". The challenge I face, is that the values from the page items are not available for the IG when it is rendered even though they have been submitted by a dynamic value. So the item values are visible in the session state, but the IG is not using them. Only after I submitted the page, they are used in the IG.

Is it possible to use references to item values in the IG or not at all? If it is, how can I do that without having to submit the page first?