Yes, it is possible to reference a worksheet tab in a different workbook. You will need to open both workbooks and use the full file path and name of the workbook that contains the worksheet tab you wish to reference. For example, to reference cell A1 in a worksheet named "Sales" in a workbook named "2019 Sales Report," located in the "Sales Data" folder on your desktop, you would type "='C:\\Users\\Username\\Desktop\\Sales Data\\[2019 Sales Report.xlsx]Sales'!A1" in the formula bar.