Dynamic externa cell link

Hello

I have several standardized excel workbooks where I want to collect data to a summarize excel workbook.

Since it is standardized I would like to make a dynamic cell reference where I in cell A1 writes the workbook name and in cell A2 write the sheet name.

This is the code I am using today.
='[Book1.xls]Sheet1'!$C$7

I would like to have it close to this:
='[A1]A2'!$C$7
In cell A1 = Book1.xls
In cell A2 = Sheet1


IS it possible?