If [condition 1] Then
           [instruction(s) 1]
Else
       If [condition 2] Then
                  [instruction(s) 2]
       Else
              [instruction(s) 3]
       End If
End If

If sglTotalAmount > 500 Then
          sglShippingCharge = 0
Else
       If sglTotalAmount > 300 Then
                sglShippingCharge = 10 
       Else
                sglShippingCharge = 15
       End If
End If