How to make it work "='C:\Users\DK-01\Desktop\["& A1 &".xlsx]Sheet1'!$A$1"

The formula below can get the value of A1 of File A and File B:
='C:\Users\DK-01\Desktop\[File A.xlsx]Sheet1'!$A$1
='C:\Users\DK-01\Desktop\[File B.xlsx]Sheet1'!$A$1

Now the value of Cell A1 and A2 is File A and File B respectively.

How to revise the dynamic link at Cell B1 and B2 to get the value of cell A1 at File A and B:

"='C:\Users\DK-01\Desktop\["&A1&".xlsx]Sheet1'!$A$1"
"='C:\Users\DK-01\Desktop\["&B1&".xlsx]Sheet1'!$A$1"

Dear Kaper,

Cell B1 can get the value of File A1 if File A1 is open.
However when File A2 is open and File A1 is closed, only cell B2 can get the value and B1 become #REF!


Please note that I have tried to get link say at cell D1,

the formula at D1 is below when File A1 is open:
='[File A1.xlsx]Sheet1'!$A$1

the formula at D1 is below when File A1 is closed:
='C:\Users\DK-01\Desktop\[File A1.xlsx]Sheet1'!$A$1

Dear Kaper,

If my excel file, that use to extract value of A1 at File A1 and A2, is at different directory, say

C:\Users\DK-01\Desktop\Scan

then the value will not become #Ref.

However, the file File A1 and File A2 should be open once; and the extracted value will become #Ref when my excel file save, exit and open again.