How To Insert Value Into IFrame Form

I am needing to build a contact form in an iframe that will change the email address the content will go to depending on the id clicked from another page. So far I am using a switch statement to choose email address based on the id clicked.

var artist
function Artist_switch(selectName) {
switch(selectName.value) {
case "p_01":
artist = xxx@xxx.com

break
case "p_02":
artist = xxx@xxx.com

break
case "p_03":
artist = xxx@xxx.com

break
case "p_04":
artist = xxx@xxx.com

break
case "p_05":
artist = xxx@xxx.com
break
}

My contact field looks like this:
<label><img src="/photo_site/artist_name.png" alt="Artist name" height="30" class="bright"/><br/></label><input type="text" class="input" name="artist_name" size="30" disabled="disabled" value="artist"/><br/>

The button on the other page:
<img src="contact.png" name="p_01"/>
How to set this up more properly?