Unfortunately, DataAssist does not employ the SQL locking capability. You can add it to the queries afterward if you want. Here's a reference on the locking capability:
In most cases however, this will be handled by the database automatically. Another way you can accomplish something like this is to add a couple of columns to the database. These would usually be LockedTime and LockedBy and then you could update those when someone accesses the page and you would check those when other users access the page and lock them out if it is within a certain time frame.