Hi.... looking for a bit of help using a shared workbook

I've got a shared workbook set-up which I have 2 or 3 people inputting information into seperatley - it all works fine except for when everyone closes the workbook and then it is re-opened it will be locked to one user (until they select 'Share Woorkbook') - is there any way it will always open up as a shared workbook?

Many Thanks