You can't, well you could technically, but not from one particular chart. And, you don't want to. Technically, you could have fifty users who could all have access to the chart at the same time.
Microsoft Access uses a file called .ldb or a locking database file for DATABASES, not charts within the database, which are open at the same time. So, if more than one user is accessing the database at one time, you should be able to see Amazingcharts.ldb in the same folder as Amazingcharts.mdb. Whenever the last user closing the database, the .ldb file will close. No data is written to the .ldb file. It is there for Access to monitor what computers and at what time they are accessing MS Access.
Imagine how frustrating it would be if a new patient registered and filled out paperwork, then gave this to your receptionist. You saw the patient, but couldn't open the chart for 15 minutes, because your receptionist had it open. Then, when you finally had a chance, your biller opened it to add the patient to billing. No, all three of you could open it, and you could print a script, while your receptionist printed demographics. All the while Access would have the database locked for these purposes.
http://support.microsoft.com/kb/208778
