如何在Visual Basic中的两个变量之间进行数学运算

        Select Case lstFlavours.SelectedItem
            Case "Vanilla" Or "Chocolate" Or "Strawberry"
                scoopType = BASIC_FLAVOUR
            Case "Mango" Or "Bananna" Or "Grape" Or "Mint Chocolate Chip"
                scoopType = PREMIUM_FLAVOUR

                scoopType*txtScoops = runningTotal 

        End Select
        Select Case lstFlavours.SelectedItem