In case you base your condition on the current date, you can use the TODAY() function in the logical_test argument of your IF formula. For example: Naturally, the Excel IF function can understand more complex logical tests, as demonstrated in the next example.
A sink mark is a local surface depression or void that typically occurs in moldings with thicker sections. They are also common in locations above ribs, bosses, or internal fillets. As the plastic cools at different rates in the mold, the surface hardens but leaves the thicker areas in the center still molten.
A sink develops similarly as a void but occurs as a surface defect rather than an internal part defect. To reduce or eliminate sink marks, packing needs to be improved either by process changes or part design changes (see description of Void for more detail).