Managing AxDatePicker events

Hello,

I have this in my user control:

<asp:TextBox ID="TextBoxPurchDate" runat="server"
                    AutoPostBack="True" ontextchanged="TextBoxPurchDate_TextChanged"></asp:TextBox>                      
<dynamics:AxDatePicker ID="DatePickPurchDate" runat="server" AutoPostBack="True"
                    TargetControlId="TextBoxPurchDate" ondateselected="PurchDateSelected" /> 

Server side code:

protected void PurchDateSelected(object sender, DateSelectedEventArgs e)
    {
        TextBoxPriceDate.Text = "Calculated stuff";            
    }

protected void TextBoxPurchDate_TextChanged(object sender, EventArgs e)
    {
        
       TextBoxPriceDate.Text = "Calculated stuff";      
    }

Despite the fact that selected date appears in TextBoxPurchDate and event PurchDateSelected fires up, the value of TextBoxPriceDate desn't get updated. I've tried to use ontextchanged event but it doesn't  fires up unless value in TextBoxPurchDate is entered using keyboard (in this caseTextBoxPriceDate is raised and TextBoxPriceDate gets updated )

How can I achieve the same when AxDatePicker is used ?

p.s. sorry for my English.