Formulas not updating if the other work book is closed

Question

I have the below formula which makes reference to another workbook in the same folder but when the file is open it just works fine, the problem is when the other excel file

Answer 1

So an simple formula would be something like:

=SUM((Auto_Zero.xlsx!MonthDB=B6)*(Auto_Zero.xlsx!CSRDB=C2))

Use Ctrl-Shift-Enter to enter the formula. Curly brackets should appear magically in the formula bar when this key-combination is used.