call object's method in javascript

Please tell me how can I call mothed provided in object in javascript.

I adopt an object in my webpage(.aspx) like this:
<OBJECT ID="logon" CLASSID="CLSID:79610275-E990-43D0-84BC-0926BA2166D8"
CODEBASE="logon.CAB#version=-1,-1,-1,-1"></OBJECT>

And I try to call funtion:GetFP() in it like this:
<script language="javascript" type="text/javascript">
function func()
{
if(document.form1.logon.GetFP())
return true;
else
return false;
}

But I failed!why? thx!!