Follow these steps to manually delete data in a cell

Press F5. Excel displays the Go To dialog box.
Click the Special button. Excel displays the Go To Special dialog box
Select the Constants radio button. The four check boxes under the Formulas option then become available. (This can be a bit confusing. Why Microsoft made the Constants radio button control some check boxes under a different radio button is not immediately clear.)
Make sure that all the check boxes under the Formulas radio button are selected. (They should be selected by default.)
Click OK. Excel selects all the constants (cells that don't contain formulas) in the worksheet.
Press the Del key.

I hope this helps!
Tim Paine