formula to refer to a cell, in a worksheet, in another workbook, that doesn't exist.

If the filename and or page names have spaces (multiple words) this will work for names with or without spaces. It is very similar to mehmeticik's formula but has " ' " around the names.

Formula:

=IFERROR(INDIRECT("'["&A1&"]"&A2&"'!"&A3),"No File Yet")