Trying to create an algorithm that takes into account multiple variables

I've hit a road block on how I can put what I have into a calculation that works. Simply I am trying to work out the "value" of each company that we have on my companies books. The information I want to put in:

Time spent on company (minutes) Time spent on paid work (minutes(can assume a value of £45 per hour for this work) Income from the company (£ and monthly) Priority - value of 1-7

The logic:

1) A client that is giving us, say arbitrarily £500 a month is twice as important as one that is giving us £250 a month.

2) I would expect a priority 1 client to give 50% more hassle than a priority 2, and a priority 2 50% more than a priority 3. The priority should have a weighting

No idea where to start :(

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I think the real issue here is that you need to determine what range of income qualifies for which priority. For example: Income [500-1000] is priority 1, Income [200-499] is priority 2, etc. Those values should not change with the data every month. – NoChance Feb 20 '12 at 21:41
It might help to make the variables disjoint. For example, your first variable might be "Time spent on pro bono (non-paid) work", since the second variable is "Time spent on paid work." Also, it's not clear to me, if you spend more time on pro bono work for company A than for company B, everything else equal, would that mean company A is more or less valuable than company B? – William DeMeo Feb 20 '12 at 21:56