Think this might solve the problem. In your workshet set a cell (A1 for example) as a reference and format it as Date i.e. Format/Cell/Date, you may have to use the Custom option and set the format as dd/mm/yy. In this cell enter =NOW(). This should give you the current date and everytime you access the workbook it will update the date. In the 'Ordered Goods' date cell enter the date of order and then go to Format/Conditional Formatting where 'Cell Value is' - 'less than' - '=A$1$-2' and then click the 'Format' button and under the 'Patterns' tab select red. If you need more days before the cell changes alter the -2 to however many days you need.
Hope that's of use.