How do you combine two forms before submitting them as one form?

I google up for the questions and got this.

<SCRIPT LANGUAGE="JavaScript"><!--
function copydata() {
    document.formthree.mytextone.value = document.formone.mytextone.value;
    document.formthree.mytexttwo.value = document.formtwo.mytexttwo.value;
    document.formthree.submit();
    return false;
}
//--></SCRIPT>

<FORM NAME="formone" onSubmit="return copydata()">
Enter some text: <INPUT TYPE="text" NAME="mytextone">
<P><INPUT TYPE="BUTTON" VALUE="Submit" onClick="copydata()">
</FORM>

<FORM NAME="formtwo" onSubmit="return copydata()">
Enter some text: <INPUT TYPE="text" NAME="mytexttwo">
<P><INPUT TYPE="BUTTON" VALUE="Submit" onClick="copydata()">
</FORM>

<FORM NAME="formthree">
<INPUT TYPE="HIDDEN" NAME="mytextone">
<INPUT TYPE="HIDDEN" NAME="mytexttwo">
</FORM>

Code (markup):

at this website :http://www.irt.org/script/190.htm

Can anyone help an give an example?

I want to combine an autoresponder form and an affiliate signup form.