Drop down selection to make an image field visible

I Am using a drop down list: with clients names that upon specific choice from list I want to make a image field visible.

Drop Down has:

Client A

Client B

Image 1 is above the drop down list, Image 2, Image 3 are below the Drop down list and all images are set to visibile

I would like to have CLient A chosen and picture in Image1, 2, and 3 become visible otherwise they remain invisible.

I am completely lost I have tried a number of codes and java but I am clearly doing everything wrong.

Can we start basic please?

Should I use Java or FOrmcalc

On what type of even? ...

SIde note this Drop down list is already linked to a number of other fields where it auto populates them with the following code:

switch(this.rawValue){

    case "":
        form1.Page1.ClientPatientCoordinator.rawValue = "";
        form1.Page1.ClientPhone.rawValue = "";
        form1.Page1.ClientFax.rawValue = "";
        form1.Page1.ClientEmail.rawValue = "";
        break;

with Javascript on Exit at Client:

And is working great now thanks for everyones help...