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.