To invert your selection of cells in Excel, you can use the keyboard shortcut "Ctrl + Shift + *". This will select the entire range of cells that are adjacent to the currently selected cells.

Here are the steps to follow:

1. Select the cells that you want to invert the selection for.
2. Press "Ctrl + Shift + *" on your keyboard. This will select all the adjacent cells to the currently selected cells.
3. Press "Ctrl + -" on your keyboard. This will bring up the "Delete" dialog box.
4. Select "Shift cells left" or "Shift cells up" depending on the orientation of your data.
5. Click "OK" to confirm the deletion.

This will delete the cells that were originally selected and leave the cells that were adjacent to them selected instead.

Alternatively, you can also use the "Go To Special" feature to invert your selection. Here's how:

1. Select the cells that you want to invert the selection for.
2. Press "Ctrl + G" on your keyboard to bring up the "Go To" dialog box.
3. Click on the "Special" button at the bottom left corner of the dialog box.
4. In the "Go To Special" dialog box, select "Blanks" and click "OK".
5. This will select all the cells that are not blank in the range, effectively inverting your selection.