lactose powder

Is there any substitute for lactose powder? any homemade recipe? or maby use box milk?
any help tks!

None that I'm aware of. Lactose is used because it's not fermented by typical beer yeasts. If you substitute another sugar it's going to ferment and you will not get the sweetness that residual lactose supplies. Maybe you could try a wine conditioner which is a blend of sugars with preservatives that prevent fermentation. But chances are you would have to go the the LHBS or order some so at that point just get the lactose.

I found today something called stevia, it is a sweet thing extract from a plant used to diabetes people, and ist not fermentable, i will try a little in my cocoa stout.

You can find it at most health food stores by the sweeteners.