Call javascript function?

hello everybody

I put this javascript in me new blog


<script language="javascript" type="text/javascript">
function showAlert() {
 alert('Hello World - this is an alert message!');
}
</script>

and wanna call it anywhere not inside the blog using flash

for example : I wanna make a flash and embed it to any website
in this flash a button with geturl to call that function

I did this but it failed :


btn.onRelease = function () { 
getURL('javascript:baseURL("http://engnajjar.blogspot.com/") & showAlert()')
}

please help me

thanks