To paste a column upside down in Microsoft Excel, you can follow these steps:

1. First, select the column that you want to copy.
2. Right-click on the selected column and choose "Copy" or use the shortcut key "Ctrl + C".
3. Next, select the cell where you want to paste the upside-down column.
4. Right-click on the selected cell and choose "Paste Special" or use the shortcut key "Ctrl + Alt + V".
5. In the "Paste Special" dialog box, select the "Transpose" option.
6. Click on "OK" to paste the column upside down.

Alternatively, you can also use the "Transpose" function to paste a column upside down. Here's how:

1. First, select the cell range where you want to paste the upside-down column.
2. Type
   Code:

   =TRANSPOSE(

   in the formula bar.
3. Select the column that you want to copy and press "Enter".
4. The column will be pasted upside down in the selected cell range.