APEX

I am having a problem retaining selected values when branching to same page.
I have a form, the first three items of which are selections based on named LOVs. The first is a Select List with Submit, which allows the user to select a "third party" using a "Third Party" LOV. The branch is to the current page and the auto-DML is conditional on this "submission" not being the the cause of the submit. The next item is a text item with the post element text calling some javascript (gleaned from this forum) to pass variables to a custom pop which allows for the selection of "contacts" associated with the selected "third party". By setting the session state to user I have tested that this context based processing works OK.
The problem I have is that when the session state is "Session", rather than "User", the first time thru the initial value of the "Third Party" item is its default (of for example) "Acme Inc". When I select "ABC & Co", the page is submitted, but on return the item has reverted back to its default value of "Acme Inc".
Could anyone advise as to what additional processing I need to incorporate to achieve my goal - to have the initial or default value displayed only when the page has been submitted via a "Create" button, and not when the submission is via one of my "Select with Submit" items.
Many thanks in advance.