Excel Object Model: Application.caller

In certain situations, application.caller returns some information on what caused the invocation of a sub or function:

application.caller is especially useful in a function that is called from a formula in cell (=func()). In that case, its value is a range that corresponds to the cell in which this formula is located.

When used in one of the four (obsolete) functions auto_open, auto_close, auto_activate and auto_deactivate, application.caller evaluates to the name of the corresponding document.