Updating Workbook cell reference based on current worksheet cell value

Greetings all,

I do a monthly KPI report. I need to reference cells from other workbooks. While the cell number doesn't change, the path does. The existing cell ref looks like this:
=sum('G:\Transportation\Driver Pay Sheet\New Pay Sheets\2019 Pay Sheets\December\[12-5-19.xlsx]KPI'!$D$72)

How can I set it up so the year, month, and date of the reference change based on the values I would input on the open KPI sheet?
I currently use control H. I have also played with (B2)\[(B4).xlsx]KPI'!$D$72) and INDIRECT. I'm having a tough time "googlesplaining" it to get a positive outcome. I'm hoping you can help. Thank you in advance.

Thank you Sweep. Unfortunately, I am getting a #ref error. I walked back through the reference and I'm not see anything missing.

I did not, but do now. Still have the ref error. I also opened a new workbook to start anew and have the same result.

INDIRECT doesn't work with closed workbook. So it's not right way to use it. The changes must be done manually or by small script.

Remark - the sum function is useless here if only one cell in the source range.