how to get/change values in fields from inside an <ext:CompositeField>

[dsmith]

when I do a Trace.Write() to find the value of a field withing a composite field, I can see the value...

Trace.Write((compositeFieldID.FindControl("textFieldID") as TextField).Text);

However, when I try to get the value or change the value in the C# code, I get an error saying the control is not defined...

(compositeFieldID.FindControl("textFieldID") as TextField).Text = "I'm here now";

I'm having this problem with a ComboBox as well as a TextField.
How can I get the value from these fields so I can use it in my code?