Here is a simple example of an event procedure. The Worksheet_Change sub is showing aging information for some input data by placing a time stamp in column A whenever a cell in row 4 to 13 has been changed. Conditional formats in A4:A13 will highlight the "age" of the corresponding rows:
Green indicates a change within the last minute
Yellow indicates a change within the last hour
Red shows a change within the last day
Please notice that the conditional format sets the background color as well as the font color to keep the time stamp data "invisible".
Please understand that this event procedure is only meant as an example. Normally I do not recommend using them. Please refer to my Excel VBA Dont's.