Can cost in TreeBagger be larger than 1?

I am using the treebagger to do classification between multi classes .But for my data, there is an important class which is easy to be predited to others.So I want to solve this problem by making the cost larger of that class.The default cost is 1(class i ~=j) and 0(class i~=j),I set one of the cost to be 2,but there is no change in myTreeBagger.cost. Can anyone help me ?