Setting listbox.multiselect state

[Steve@GIHS]

I have one listbox that is populated with a range of data based on the users selection. The listbox is required to have two states :

Multiselect = None

or

Multiselect = Extended.

How is this set in VB for application ? I tried Me.lst_Data.Multiselect = 2 but get an error "Invalid use of property.

Thanks