OlkComboBox.TopIndex Property (Outlook)
Returns or sets a Long that represents the index of the item at the top of the displayed portion of the list in the combo box. Read/write.
expression A variable that represents an OlkComboBox object.
As the list scrolls, the item at the top of the list will change, and the value of this property will change to reflect the item currently displayed at the top of the list.
The index value is zero-based. The default value is -1, indicating that no special ordering should be applied.