Returns the name of the table that contains the field that has the focus.
If there is no active field, this function returns an empty string.
There are two fields, Teachers::Name and Coaches::Name, on the current
layout. Creating a script that returns the result of
Get(ActiveFieldTableName) to a third field will return
Teachers when the script is performed after clicking in the Teachers::Name field, or will return
Coaches after clicking in the Coaches::Name field.