Updating Custom Function

I have a basic custom function to include the full file path and name in cell like such.

Function FilePathName() As String
    Dim FName As String
    
    FName = ThisWorkbook.FullName
    FilePathName = Replace(FName, "\", "\\")

End Function

But when I either move or rename the file, I want the cell value to update to the current folder/file name structure automatically. And I only want to update this one specific worksheet or named ranged, and not the entire workbook as it slows down the opening of the file. I've tried using the below in the workbook module but it does not update the cells.

Private Sub Workbook_Open()

    'ReCalculate Chartlinks get current file path
    Sheets("ChartLinks").Range("ChartNames").Calculate
'
End Sub

I did try changing the above to use CalculateFull and Excel throws a run time error. So what is the trick to updating a selected worksheet or named range in VBA without updating the entire sheet?

Well.

I found a way to do this using built in excel formula's like such. but there still could be an easier way, but I did need t e double \\ in the file path for OLE link in Word.

'Gives the File Path on line E2
=LEFT(CELL("filename"),FIND("[",CELL("filename"),1)-1)

'Gives the FileName on Line F2
=MID(CELL("filename"),SEARCH("[",CELL("filename"))+1, SEARCH("]",CELL("filename"))-SEARCH("[",CELL("filename"))-1)

'Combine it together with Substitute
=SUBSTITUTE(E2,"\","\\")&F2

That give me something like C:\\Data\\Folder\\myfile.xlsx.