ADX formula

["etrader" <etrader@xxxxxxxxxx>]

Hello,

Does anyone know have a formula for calculation of
ADX so that i can apply it on a 5min chart to
determine whether ADX on the equivalent 30,60 min
chart is above 30 threshold?

For example, if I apply a Average(Close,240) on a
5min chart it will plot  equivalent values as
Average(Close,20) on a 60 min chart.  The reason
why this works in this case is because Average is
a linear function.  I cannot do the equivalent on
ADX because it is non-linear.

Does anyone have any suggestions?

Thanks,
Bing