Costing of lost man hours

I'm a computer support consultant and often see staff at client's of mine battling with bombed out old PCs, their bosses just tell them to make do with what they got. Now I know this is costing them a packet, I just need to be able to show their financial departments exactly what it's costing them. I'm looking to run this in PHP on a Linux hosting server, we have our own hosting environment so I'd like this to be online, you can use anything you like provided it runs on our server. This will require knowledge of which cost factors to build into the calculation. i.e. office space rental percentage of space used by an individual, compared to the amount of staff working in the company. a particular staff member's salary etc. etc. These need to be fields that the Financial director fills in and is then able to click on Calculate and he/she must see what it's costing by the hour, by the day and by the month to have a staff member sitting around waiting for computer equipment to boot up, open and close documents etc etc. The system must be able to e-mail results to person filling in the sheet, ideally they should be filling in all their details before they start, including their e-mail details, the results to be sent to them. and BCC to us of course. To qualify for this project you will need to show me what cost factors you would build into this system, having previous experience will also be benificial.