Is a 3 nested dropdpwnlist achievable?

[rote]

I have a 3 dropdownlist and a gridview to display..
What i want is if i load the page i want all the dropdownlist and the
Gridview to get populated and linked on the fly.

But my problem now is when i load the page i want all the dropdownlist
should be populated and linked automatically.
but it doesn't .The first 2 works the last dropdownlist is empty and the
gridview shows nothing..
Any ideas what 'm doing wrong?

All the 3 dropdownlist are linked like so below
<table>

<p>

<tr>

<td>

Select a Dealer

</td>

<td>

<asp:DropDownLi st ID="ddlDealer" runat="server" AutoPostBack="T rue"
DataSourceID="S qlDataSource4"

DataTextField=" dealer" DataValueField= "dealer">

</asp:DropDownLis t>

<asp:Label ID="Label1" runat="server"> </asp:Label>

<asp:SqlDataSou rce ID="SqlDataSour ce4" runat="server" ConnectionStrin g="<%$
ConnectionStrin gs:cn %>"

SelectCommand=" spGetDealer"
SelectCommandTy pe="StoredProce dure"></asp:SqlDataSour ce>

</td>

</tr>



<tr>

<td>

Select a Master Code

</td>

<td>

<asp:DropDownLi st ID="ddlMaster" runat="server"
DataSourceID="S qlDataSource1" DataTextField=" Master_Code"

DataValueField= "mc_id"
OnSelectedIndex Changed="ddlMas ter_SelectedInd exChanged"

AutoPostBack="t rue">

</asp:DropDownLis t>


<asp:SqlDataSou rce ID="SqlDataSour ce1" runat="server" ConnectionStrin g="<%$
ConnectionStrin gs:cn %>"

SelectCommand="[spGetAllSchedul eMaster]"
SelectCommandTy pe="StoredProce dure">

<SelectParamete rs>

<asp:ControlPar ameter ControlID="ddlD ealer" Name="dealer"
PropertyName="S electedValue"

Type="string" />

</SelectParameter s>

</asp:SqlDataSour ce>

</td>

</tr>


<tr>

<td>

Select a Plan Value

</td>

<td>

<asp:DropDownLi st ID="ddlPlans" runat="server" AutoPostBack="T rue"
DataSourceID="S qlDataSource2"

DataTextField=" Plan Code" DataValueField= "plan_id"
OnDataBound="dd lPlans_DataBoun d">

</asp:DropDownLis t>


<asp:SqlDataSou rce ID="SqlDataSour ce2" runat="server" ConnectionStrin g="<%$
ConnectionStrin gs:cn %>"

SelectCommand=" spGetPlanValues ByID" SelectCommandTy pe="StoredProce dure">

<SelectParamete rs>

<asp:ControlPar ameter ControlID="ddlM aster" Name="mc_id"
PropertyName="S electedValue"

Type="Int32" />

</SelectParameter s>

</asp:SqlDataSour ce>

</td>

</tr>

</table>