How can I change the list height for a ComboBox?

[mccoyn]

I am making a class dervied from ComboBox. The height of the items in the list will be changed by the program. I've gotten this to work with OnMeasureItem, but there is a large space left behind. For example, if their originally was 10 items each with a height of 20 and I changed the height of all of them to 10, then their would be a space of 100 that is blank and unselectable. I am using the following properties

mycombobox->DrawMode = DrawMode::OwnerDrawVariable
mycombobox->DropDownStyle = ComboBoxStyle::DropDownList

I'd like a function like the following

void MyComboBox::FixComboBoxListHeight()
int idx
int total_height

total_height = 0
for(idx=0; idx < Items->Count; idx++)
total_height += GetItemHeight(idx)
SetListHeight(total_height); /* I can't figure out how to do this. *
Any ideas