IMPORTRANGE to refer the function but not the value/result

Thanks for the help

Here is my situationThere are 5 different spreadsheets, i.e. Master, 1, 2, 3, 4)

All cell A1 in 5 different spreadsheet has the same function e.g. =count(B1:B5), they count the data in their own spreadsheet.

And I want to change the function =count(B1:B5) to =count(B1:B20) in all files (Spreadsheet 1,2,3,4)

IMPORTRANGE can only refer the value/data/result of Cell A1 in Spreadsheet Master but not the function

Is there any other functions to automate the change for all Cell A1 of all Spreadsheet 1,2,3,4 when I change the function in Spreadsheet Master Cell A1?

Thank you very much