COUNTIFS #VALUE error because workbook is not open. How can I fix this?

[jelle1100]

=COUNTIFS('\\aweta\user\profile\jooms\Desktop\[Sofon-sheet.xlsm]New'!$M$2:$M$93356;$C$1;'\\aweta\user\profile\jooms\Desktop\[Sofon-sheet.xlsm]New'!$P$2:$P$93356;">="&$D$2;'\\aweta\user\profile\jooms\Desktop\[Sofon-sheet.xlsm]New'!$P$2:$P$93356;"<="&$E$2)

When I open my main sheet (called "2016") I can choose to update, not update or cancel. I then choose to update and the value error appears. When I open "Sofon-sheet" everything is good and there are no more value errors.

How can I make sure that this error doesn't happen again?

 

[AliGW]

Make sure that the referenced workbook is always open when you open this one.

 

[jelle1100]

Maybe my problem is a bit more difficult than it seems.
I have about 50 different sheets on different pc's all called "2016". Every "2016" sheet has this formula:
=COUNTIFS('\\aweta\user\profile\jooms\Desktop\[Sofon-sheet.xlsm]New'!$M$2:$M$93356;$C$1;'\\aweta\user\profile\jooms\Desktop\[Sofon-sheet.xlsm]New'!$P$2:$P$93356;">="&$D$2;'\\aweta\user\profile\jooms\Desktop\[Sofon-sheet.xlsm]New'!$P$2:$P$93356;"<="&$E$2)

The Sofon-sheet has to be on a permanent directory so that every "2016" sheet can call on this information. It is impossible to have the Sofon-sheets always open, or at least, I don't know how to.
Some articles say SUMPRODUCT works, because it can look in closed workbooks. Can I do something similar? I need this connection, but it cannot stay open.
thank you