If you have two Excel spreadsheets, you can link cells between them. Using the Excel Paste Special option, you can paste a link from a cell in one spreadsheet into a cell in another. You can carry this process out both ways, linking between the two spreadsheets. When you make a change to a cell linked in another spreadsheet and save the altered spreadsheet, the next time you open the other spreadsheet with the pasted link in it, the linked cell will update.
Preparing to link
You must first have the two spreadsheets open in Excel at the same time. You can link between the cells using a similar technique to the one you could use to link between cells in the same spreadsheet or workbook. To link a cell in one spreadsheet to a cell in another, you need to locate the first cell you wish to use as source, select it and choose "Copy" to get it saved in the clipboard.
When a cell has been placed onto the clipboard, it is ready to be pasted into another spreadsheet. Switch to the other spreadsheet and select the cell you wish to paste the link into. By selecting the "Edit" menu then "Paste Special" you can choose pasting options to link the two cells.
The "Paste Special" options in Excel allow you to select the details of how your cells are linked. Selecting "All" under "Paste" will copy the data value in the copied cell, whether it involves a formula or not, plus the cell border formatting. If you only want to paste the cell data value, not the cell border, select "All except borders" instead of "All." Either of these options should make the "Paste Link" option become available, as it relies on the user selecting either "All" or "All except borders." Selecting "Paste Link" will copy the location of the copied cell and the name of the file it is contained within. This means that the linked cell will only function correctly as long as the source file remains in the same location.
Once you have a cell linked from one spreadsheet to another, you can carry out the same process in the opposite direction. By selecting the source data you want to copy in the second spreadsheet, you can then switch back to the first one and choose "Paste Special" options to link the cells. Once you have the two files linked using the reference to the file locations as well as cell locations within the files, any relevant changes in one spreadsheet will be reflected the next time you open the other one.