Sumproduct formula returning #Value! error

Hi,

I'm trying to figure out how to do a sumif or sumproduct between two different workbooks. Originally, I used the sumif formula, but when I closed one workbook, the other workbook with the sumif formula would show #Value! error. I know that you can use the sumproduct formula to fix this problem, but I can't seem to get the sumproduct formula to work correctly. I have tried different ways of writing the sumproduct formula, but it still gives me the #Value! error.

Here's one of my sumproduct formula between two different workbooks:

SUMPRODUCT(--('[2014 Strat Plan HR Investments.xlsx]PO Investment'!$C$13:$D$54=$C8),'[2014 Strat Plan HR Investments.xlsx]PO Investment'!Z$13:Z$54)

Workbook 1: 2014 Strat Plan HR Investments v2 - test.xlsx (this is where I want the sumproduct formula to be)

Workbook 2: 2014 Strat Plan HR Investments.xlsx (this is where I want the value to pick up)

Any help is appreciated!

Thanks

Here's the sumif formula that returns a value between two different workbooks:
=SUMIF('[2014 Strat Plan HR Investments.xlsx]PO Investment'!$C$13:$D$54,$C8,'[2014 Strat Plan HR Investments.xlsx]PO Investment'!Z$13:Z$54)

However, when the workbook that contains the data closes, the other workbook that has the sumif formula returns the #Value! error. I don't want to reopen the two workbooks everytime I want the values to populate. I want to take the above sumif formula and embed the sumproduct formula into it to fix this problem.

I have attached the two workbooks. Workbook "2014 STrat Plan HR Investments v2 - test.xlsx contains the sumif formula (cell G8) and it's highlighted in yellow.

Your sumproduct formula works. I don't have to open the data file to update the links and the #Value! error is not there anymore.

Thanks for your help!