A formula is an expression which calculates the value of a cell. Functions are predefined formulas and are already available in Excel. To count the number of cells that contain numbers, use the COUNT function. Note: use COUNTBLANK to count blank cells and COUNTA to count all cells...Instead of using normal cell references, we are going to use row and column references and we are referring to how many rows or columns we are away from the ‘hours worked’ cell. The formula that actually gets added to the sheet will be in the normal format, i.e. column letter and row number (e.g. B15-B14).