automatic fill with external references

I need to use a few spreadsheets with one sheet for every client. I want to introduce the references to their cells into a new file.
Then, on the new file I will have
=‘file:///home/utente/file1.xls’#$Foglio1.$B$4

as the reference to the B4 cell in sheet 1 of my file1

How can I compile a column changing the reference only to the sheet?

I need to have a series with

=‘file:///home/utente/file1.xls’#$Foglio2.$B$4
=‘file:///home/utente/file1.xls’#$Foglio3.$B$4
=‘file:///home/utente/file1.xls’#$Foglio4.$B$4

and so on.

Nonsono riuscito a trovare un modo ma sono sicuro che ci deve essere un sistema senza dover riempire a mano cella per cella