InfoPath Dev

I have a form created using infopath 2010, and published to the SP 365 form library.

The form will have multiple users editing existing data in the form.  THe way it works is like this

1. User raised a new ECO request (form), completes some preliminary data and saves.

The manager of the person that raised the form then accesses the same form, and selects his/her name and ticks an approved to proceed box.

This box, once ticked opens out other sections of the form where other users are assigned tasks to complete.

He then completes the other parts of the form, and submiuts it, essentially updating the existing data on SP

Others then access the same form, tick the box relevant to their task as completed and so it goes on until all relevant tasks are completed

This all works, bar one part.  Each time the form is created and then saved, I have a small calculation (Concat) that gives the form a name, using the ID + 1 function to increment this ID each time a form is created, and this also works, however when a form has been raised, and is called ECO-0002, someone opens that form and the form they open contains all the information from creator but the ECO id is now 0003, so when I hit submit I end up with a second form using the new ID number.

The form is web enabled use only, so how do I allow users to open an existing form and update data in the form then save that new data to the same form.

I have a scenario where people can create a new form or edit an existing one. I created a field called SUBMIT that would be set to FALSE by default when the form is created. When they 'saved' the new form I would check to see if SUBMIT was TRUE or FALSE, if FALSE then I saved the new form with a unique name and would automatically change the SUBMIT field to True. If they opened a form that already existed the SUBMIT field would be True, so I would save the form with the same name. If False, a unique name. Does that make sense?