How to access multiple field templates in another field template and in insert page of asp dynamic data?

Hi,

I am working on asp dynamic data
I am using FormView in my Insert page as following


   
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I am using some existing field templates and some custom field templates.
In my form the following fields are available

[DropDownList1]

[TextBox1]

[TextBox2]

[DropDownList2]

My requirement is 
1) how to get these object in my insetr page code behind(insert.cs) ?
and
2)I have created field template with DropDownList in this fieldtemplate
I want to access remaing fields objects in this field template.
For example in selectIndexchanged event procedure I want to set values for remaining fields(field templates) 
Can you tel me how to do this ?

Thanks,