Create design contrast matrix using automatic function

Question

I would like to create a function that return design contrast matrix of factors with number of factors, levels in each factor as input. Im my example, I have:

1st factor

treat <- gl(3, 20, labels = paste("t", 1:3, sep=""))

2nd factor

imp <- rep(gl(2, 10, labels = c("yes", "no")), 3)

create a design matrix of the contrasts for "imp"

contrasts(imp) <- c(-1, 1)
Imp <- model.matrix(~ imp)[, -1]

create a design matrix of the contrasts for "treat"

contrasts(treat) <- cbind(c(0,1,0),c(0,0,1))
Treat <- model.matrix(~ treat)[, -1]

Now I ask how I can start for create Imp and Treat matrix and all combination of Imp and Treat, given Factor=2, Levels = c(3,2) and Nsize=60, for example?