setting a variable for monthly reports

I have a monthly report I need to generate.

The data resides in 12 different spreadsheets named January - December within the same workbook.

I have a 13th spreadsheet where I would like to pull the monthly data for my reports.

I only need to pull data a month at a time so I need a variable to address the different spreadsheet(month).

Welcome to forum

Can you upload sample file?