Conditional formatting based on multiple conditions

I am using a spreadsheet to track machine downtimes at a large manufacturing plant. The machines are identified by a four digit number and are listed in column D and their respective downtimes are in column F. I would like to set the spreadsheet up so that if the same machine is down for a certain amount of time (say 16 hrs) all the rows which contain that machines 4 digit number are highlighted yellow and if the machine is down for 20 hours the rows are highlighted red. The spreadsheet may possibly be tracking hundreds of machines so if there is a way for a macro to automatically look at entries with the same 4 digit identifying number, evaluate and possibly highlight them without me physically entering all the machine numbers into the code that would be ideal. I've attached a sample file. I have very little experience with VBA and this definately above my head. Please help.