This is not an excel specific issue as I've seen the Clipboard warning whenever you copy large data from other applications as well.
However, when using excel, you might have a few ways to work around it using VBA.
There are several methods for preventing the display of this warning message. The quickest manual method is to press the ESC key just before you close the workbook.
In an automated scenario that uses a Visual Basic for Applications macro to cut or copy cells, you may not consider it an acceptable option to press the ESC key to prevent the warning. In that case, use any of the following programmatic methods to prevent the warning.
Method 1: Copy A Single Cell
If you are using Visual Basic for Applications macro to cut or copy cells, insert the following line immediately before the line that closes the workbook:
ActiveSheet.Range("A1").Copy
The warning message is not displayed if the Clipboard contains 100 or fewer cells.
Method 2: Exit from CutCopyMode
If you are using Visual Basic for Applications macro to cut or copy cells, insert the following line immediately before the line that closes the workbook
workbook.Application.CutCopyMode = False
where "workbook" is your workbook object.
NOTE: By setting CutCopyMode to True or False, Excel may cancel Cut or Copy mode.
Method 3: Save the Workbook
If you are using Visual Basic for Applications macro to cut or copy cells, insert the following line immediately before the line that closes the workbook
workbook.Save
where "workbook" is your workbook object. When you save a workbook, Excel is no longer in Cut or Copy mode.