Is there some sort of query possible in MS Access to insert a row but if it violates the contraints that if will update the row then with these constraints. I know other db systems have this option but I can't get something like that working in MS Access.
This is informally known as an UPSERT (try googling), although the ISO SQL syntax uses the MERGE keyword.
In short, no - you have to code it up yourself using VBA. You can't perform this solely in Access SQL. Personally, I would code it to avoid getting an error since error handling has some overhead.