How to see portfolio performance over x period?

[MarkD]

Is there any way that i can see how my portfolio has performed over, say, 12 months, or 6 months? I get the basic view which shows me current % "for all time" but I want more concrete ways to measure performance. Can this be done?

[BC02]

the best way is to determine this is to (total portfolio value / total contributions). Square root this value with the years you've invested (excel you can write [ =POWER((value/contrib), 1/yrs)-1 ]