3 dropdown menus to auto populate 1 textbox depending on selection

Update: if this makes my end goal more clear:

I have 3 different dropdown boxes

• Sponsorship Level
• Ad Size
• Premium Positioning

I need the dropdowns to feed into 1 text box 

• Cost

The ideal is to code this in a way where the each dropdown option would be able to have a numerical value conencted to it in the coding and add up as they choose their options. 

On top of this, I would like to have the dropdown influence other dropdown menus. 

Meaning: 

Sponsorship Levels:

If you choose :

Production Sponsor (Musical) then the Ad Size option would be FULL PAGE (4.67"w x7.67"h) COLOR and the Premium Position options would be  Back Cover, Front Inside Cover, Back Inside Cover

etc...

Don't use a switch command. Use an if statement with multiple conditions, like this:

var v1 = this.getField("Dropdown1").valueAsString;
var v2 = this.getField("Dropdown1").valueAsString;
var v3 = this.getField("Dropdown1").valueAsString;

if (v1=="A" && v2=="A" && v3=="A") event.value = "A-A-A";
else if (v1=="A" && v2=="A" && v3=="B") event.value = "A-A-B";
else if (v1=="B" && v2=="A" && v3=="C") event.value = "B-A-C";
// etc.
else event.value = "";