How calculate Average

Hello,

I have a calculation of a KPI that should take the average of the Year to Date (YtD) value of another KPI and I don't know how to do it.

I know how to do a YtD value but not the average of this YtD value.

For every month:

KPI B = average (YtD of KPI A)

where KPI A is a decimal number calculated by hierarchy of 2 other KPIs input.

So for every month we divide the YtD value by the number of months passed since the beginning of the year.

To be clearer, I give you an example:

Let's calculate KPI B for April (4 months)

            Jan     Feb     March      April        YtD (April)

KPI A    10      15          15          20          60

So with the formula above:

In April,  KPI B = 15 = YtD/4 months = 60/4 

Let's calculate KPI B for June (6 months):

            Jan     Feb     March      April      May     June    YtD (June)

KPI A    10      15          15          20       30          30      120

So with the formula above:

In June,  KPI B =   20  =  YtD/6months = 120/6   

Any help would be appreciated.

Thanks in advance.