Time adjustment formula

[cwgiant]

I am having some computer issues and have lost my excel spreadsheet that I had some formulas on.
I am looking for a formula for time adjustments.
I am not looking for ANY theory or OPINIONS about time adjustments.
The scenario is simply: sale 1 sold for $350,000 on 01/01/08 and sale 2 sold for $300,000 on 06/01/08. What is the correct mathematical formula for determining a price difference based on a monthly factor? Again, make no assumptions about anything; please just help me properly reconstruct my formula.
Thank you very much for your help, I am grateful and appreciative.

 

[Old Man]

Month avg sp - previous month avgsp = x$
x$ / month asp = %+/-
total %+/- (sale date to present) = adj amt

 

[Dan/Fla]

There is a formula for a time adjustment which will work for all assignments? I have been spending time abstracting increases, or declines in each market for no reason Wow I would like to see those too. Here in this area Newer condos values are changing faster than S/D with builder still in building homes which values are changing faster than older established neighborhoods, at least that is what I thought I had found. I have been spending time adjustments, abstracting on a market by market basis and I could have saved all that work with a time adjustment formulas. Please let me know those formulas, too.

 

[Kali the Boston Terrier]

Rate of change = (old price-new price)/new price
Monthly Rate of Change = Rate of Change/#months

and no editorial