Basically, when you open a file your computer locks it so your changes get saved over anyone else who may try to change it while you have it open. As far as I know, you cannot do as you described to switch which user gets to write to the file without closing the file.
BUT you may be able to use the shared workbook feature to allow collaboration of a networked file via multiple people.
If you need input from several people, you can create a shared
workbook and place it on a network location where they can edit it
Here information about shared workbooks.