질문의 요점을 이해를 못해서, ^ ^;; 이게 아닌가 싶네요.

index.htm
<iframe name=a id=a src='./a.htm' width=222 height=222 frameborder='0' topmargin='0' leftmargin='0' marginheight='0' marginwidth='0'></iframe>
<iframe name=b id=b src='./b.htm' width=222 height=222 frameborder='0' topmargin='0' leftmargin='0' marginheight='0' marginwidth='0'></iframe>


a.htm
<A href="./b.htm" target="b">b</A>
<A href="./c.htm" target="b">c</A>


b.htm
b


c.htm
c