If you want to store the Excel file in a macro-free workbook format, you should avoid both VBA and macros (i.e. the XL4/XLM approaches suggested in other answers). In this answer, I made the assumption of a macro-free Excel file.
If you use MS-Excel 2013, you can use:
If you use older MS-Excel versions (e.g. 2010, 2007), there is no true function to determine if a cell contains a formula. However, you can approximate it using:
The function above returns:
- TRUE for cells containing a formula wich results in a String data.
- FALSE for cells containing a String literal or is blank.
- "MAYBE" for cells containing a boolean, a number or a date, no matter if this value is literal or the result of a formula.