To invert the selection of cells in Microsoft Excel 2007, you can follow these steps:

1. Select the cell or range of cells that you want to exclude from the selection. In this case, select cell A1.
2. Press and hold down the Shift key on your keyboard.
3. Click on any other cell or range of cells that you want to include in the selection. This will add those cells to the selection while excluding the originally selected cell or range.
4. Release the Shift key.

Now you should have inverted the selection of cells in Excel 2007. All cells except the originally selected cell or range should be highlighted. You can then perform any desired actions on the selected cells, such as formatting or data entry.