EViews.com

Could you please explain me how to perform an estimation of a restricted equation? It should be an OLS estimation with 7 factors (X=c(1)+c(2)*a+c(3)*b+c(4)*c+c(5)d+c(6)*e+c(7)f) and the restriction that all factors sum up to 1 and that each factor is not negative. How do I store this equation in evi...