Dropdowns have a special onAction callback that return the index of the selected item
You can use the same for all 3 drop downs and Select Case on control.ID
Sub ddOnAction(control As IRibbonControl, id As String, index As Integer)
Select Case control.id
Case "dd01"
MsgBox "Drop Down#1 (" & control.id & ") MenuID = " & id & " Item# = " & index
Case "dd02"
MsgBox "Drop Down#2 (" & control.id & ") MenuID = " & id & " Item# = " & index
Case "dd03"
MsgBox "Drop Down#3 (" & control.id & ") MenuID = " & id & " Item# = " & index
End SelectEnd Sub