Linear Regression with a data set array

I have a data set variable, that contains multiple column vectors. Say DS(Demand, Price, Income). I want to regress Demand against Income; but I want to be able to reference the vectors in the data set in the regression function itself. Eg. b=regress(Y,X) becomes b = regress(DS.Demand, DS.Income) - what is the correct syntax for doing this? Thanks Chet