Time Weighted Standard Dev

#1
I have a data set that looks like this:
Fin Svcs Fin Svcs
Date Banks US Banks Yankee
18-Jun-2009 336.48573 285.98085
17-Jun-2009 339.12881 284.21639
16-Jun-2009 334.81054 281.07956
15-Jun-2009 330.36172 280.58574
12-Jun-2009 330.70681 280.16293
11-Jun-2009 330.59932 280.10058
10-Jun-2009 330.84413 282.97856
09-Jun-2009 334.85719 290.5655
08-Jun-2009 336.19021 293.43674

I want to calculated the standard deviation for this data going back 60 days. However, the most recent deviations are much more significant than the deviations going back 60 days. How can I create a standard deviation function on excel that will put more weight on the most recent data point?
Thanks