Identify Ajax Proc Name From A String Variable

The best way to describe what im trying to accomplish is with a code
snippet. Im using the free .NET ajax library.

<script language='javascript'>
function proc1()
{
myFunc("MyCodeBehind.MyAjaxProc");
}
function myFunc(procName)
{
procName("My Parameter", processMyFunc);
}
function processMyFunc(response)
{
// Process response from the server
}
</script>

So im essentially invoking an Ajax function , but I cant explicitly use
the name of it like so

MyCodeBehind.MyAjaxProc("My Parameter", processMyFunc);

That line would work fine. Clearly though, this doesnt work

var procName = "MyCodeBehind";
procName("My Parameter", processMyFunc);