Automatic update of reference to cell in another calc file

New on LibreOffice. Just migrated from MS. Sorry if this is too easy, but I can’t find the solution.
Simplified example: I have a Calc file A with som numbers and a sum in cell C15.
Then I have another Calc file B, where I reference that sum, i.e. cell C15 in file A.
Then I go into file A and insert one row under row 4, so the sum is now in cell C16.
I would expect the reference in file B to pick up un this, so it now references C16 in file A, but it seems it is still referencing cell C15, which no longer contains the sum.
What am I doing wrong?

maybe try Named Ranges and Expressions

Thanks, but it seems I can’t insert a named range from another file. I can only insert in the same sheet as where the name is defined.

yep. tricky : 145994 – references to named ranges in external files do not update on document open #c10