can you determine which txtfields are required by a selection in a dropdown?

 I am creating an online application but trying to figure what would be the easiest way and the most effecient way of doing this?
I have an online credit application that can either be for an Individual, LLC, partnership or Corporation.  each one of these have different required fields.  would it be possible to make certain fields required by which selection they make in this drop down:
<asp:DropDownList ID="DropDownList2" runat="server"> <asp:ListItem Text="LLC" Value="0"></asp:ListItem> <asp:ListItem Text="Individual" Value="1"></asp:ListItem> <asp:ListItem Text="Corporation" Value="2"></asp:ListItem> <asp:ListItem Text="Partnership" Value="3"></asp:ListItem> <asp:ListItem Text="Please select one. ...