INDEX with dynamic File Path String

Hello, I was trying to create a table with values from another workbook. I wonder if there is a way to reference part of the filepath linking to an existing excel value.

For instance, a regular excel value from another workbook can be: ='\\data\my folder\[20160914 Project Summary'!$T$2
I would like to automate the process by making the link equal to ="\\data\my folder\["&Q4&" Project Summary'!$T$2" where Q4 can be a variable. So every time I change Q4, the filepath automatically updates to the new location.
The INDIRECT function would not work because it won't work on closed workbooks.

Thanks a lot for your help!