How to call function when enter is pressed in text area?

Im trying to send information for a login system with two textfields, when i press login it sends the information perfectly but if I press enter it doesnt work. How can I detect this event with the enter key properly?

Ive got this so far:

 #pragma strict
 
 function Start () {
     
 }
 
 function Update () {
     if(Input.GetKeyDown("enter")){
         enterPressed = true;
     } else {
         enterPressed = false;
     }
 }
 
 var enterPressed : boolean = false;
 var Username : String = "";
 var Password : String = "";
 var loginSuc : boolean = false;
 var stringText : String = "";
 var loggedinUser : String = "Guest";
 
 
 function OnGUI () {
 
     GUI.Label (Rect (380, 380, 100, 750), "Username");
     Username = GUI.TextField (Rect (380, 400, 200, 25), Username, 25);
     
     GUI.Label (Rect (380, 425, 100, 750), "Password");
     Password = GUI.PasswordField(Rect(380,445,200,25), Password,"*"[0],25);  
     
     if (GUI.Button (Rect (445, 480, 70, 25), "Login") || enterPressed == true)
     {
          checkPassword();
          print ("Button pressed");
     }
     
 
     GUI.Label (Rect (440, 260, 120, 750), stringText);
     
     GUI.Label (Rect (800, 60, 90, 50), "You are logged in as "+ loggedinUser);
     
 }
 
 function checkPassword(){
     //set the WWWForm to send to the PHP page
     var sendLoginInfo : WWWForm = new WWWForm();
        sendLoginInfo.AddField("Username",Username);
        sendLoginInfo.AddField("Password",Password);
 
     //send the WWWForm via WWW
     var getdata : WWW = new WWW("login.php",sendLoginInfo);
     yield getdata; //Wait for the data to return
 
     //if TRUE >> Load level    
     if (getdata.text == "true") {
         login();
     } else {
         stringText = "Login Failed!";
     }
 }
 
 function login(){
     stringText = "Login Successful!";
     loggedinUser = Username;
 }