It is all possible, but I am not sure what exactly you are asking. Is this it?
function subForm(){
magString = ""
for (x=0; x<document.myForm.elements.length; x++){
if (document.myForm.elements[x].type == "checkbox"

{
if (document.myForm.elements[x].checked){
magString += ", " + document.myForm.elements[x].name
}
}
}
if (magString.length > 0){
magString = magString.substr(2) //peel off first comma
document.myForm.action = "mailTo: myEmail@mydomain.com?subject=Magazine subscriptions - " + magString
document.myForm.submit()
}
else{
alert("Please select at lease one magazine."

}
}
</script>
<form name="myForm">
<input type=checkbox name="Time">
<input type=checkbox name="NewsDay">
<input type=checkbox name="PC Mag">
<input type=button value="Submit" onClick="subForm()">
Programming today is a race between software engineers striving to build better and bigger idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning. - Rich Cook