Formula with cell reference in file path

I have a number of cells that pick up from another location e.g.
=+H:\budget\period1\(accounts)sheet1'!$B$720

I want to copy this forumla to pick up other periods (period2, period3 etc). I can do a find and replace but this is tedious. Is there a way to make the "period1" reference dynamic so I can pick this bit of the forumla up from another cell. Then I can create my "periodX" names in a single line and not have to go through the find/replace process?

You can do it with a function, but the native Excel function required the other workbook to be opened.

=INDIRECT("'H:\budget\"&A1&"\[accounts.xls]sheet1'!$B$720")

To do it with closed workbooks, you need to download and install a free adding from here: Morefunc

and use: =INDIRECT.EXT("'H:\budget\"&A1&"\[accounts.xls]sheet1'!$B$720")