how do i get a value of a painting by helen van wyk?

Question

Found an old painting in my attic of my Aunt who was a friend of the artist. Its a portrait and is aprox. 17 by 21.

Answer 1

http://www.askart.com/askart/v/helen_van_wyk/helen_van_wyk.aspx

There is all the info you could want including appraisals.