To create a mixture amounts design
main topic
    
see also 

1    In the Create Mixture Design dialog box, click Components.

2    Under Total Mixture Amount, choose Multiple totals and enter up to five mixture totals. Suppose you are testing plant food and would like evaluate plant growth when one gram versus two grams of food are applied. You would enter 1 2. Click OK.

More

For a complete discussion of mixture-amounts experiments, see [1] and [2].