Ibra,

You would need to adjust the margin. Margin controls how much you are actually trading with. Capital just ensures that on that margin amount your account can survive. If starting capital is $100, and margin for that system is $10, and you want to trade $2000 instead of $100, then $2000/$100*$10 = $200. So...if you want to use 20 times the capital, then you use 20 times the margin.