ComboBox sorting

[C++ Programming]

Hi,
I am new bie to Dialog Based,
I have a combobox and i am reading some values from it.
For ex : the values are a,aa,aaa,b,bb,bbb
I have set the properties as DropDown,Sort and verticalScroll.
If i enter the any value in editbox.
For ex if i enter "a" in edit box.
I have to get values in sorted
Ex a,aa,aaa

Any help appreciated

Thanks
Raj