When you click on the back button in the onepage steps, you are calling a js prototype method Checkout.prototype.back() (see skin/frontend/base/default/js/opcheckout.js:245).

So, one way to modify the actual behaviour is to override this method :

1. If not already done, copy in your theme the file app/design/frontend/base-or-rwd/default/template/checkout/onepage.phtml. Then, after the line

   getSkinUrl('js/opcheckout.js') ?>">

Add the following line to add your own js file (that we will create soon) :

<script type="text/javascript" src="<?php echo $this->getSkinUrl('js/opcheckout-override.js') ?>"></script>

2. In your theme, create the file skin/frontend/<your-theme>/default/js/opcheckout-override.js.

3. In this file, we have to override the Checkout.prototype.back() method. I did not test it but we could write something like :

   Checkout.prototype.back = Checkout.prototype.back.wrap(function(parentMethod) {

    if (this.loadWaiting) return;
   
    if(this.currentStep == 'shipping_method'){
        this.changeSection('opc-billing');
    }
    else{
       parentMethod();
    }
   

   });

Hope it helps.

When you click on the back button in the onepage steps, you are calling a js prototype method Checkout.prototype.back() (see skin/frontend/base/default/js/opcheckout.js:245).

So, one way to modify the actual behaviour is to override this method :

1. If not already done, copy in your theme the file app/design/frontend/base-or-rwd/default/template/checkout/onepage.phtml. Then, after the line

   getSkinUrl('js/opcheckout.js') ?>">

Add the following line to add your own js file (that we will create soon) :

<script type="text/javascript" src="<?php echo $this->getSkinUrl('js/opcheckout-override.js') ?>"></script>

2. In your theme, create the file skin/frontend/<your-package>/<your-theme>/js/opcheckout-override.js.

3. In this file, we have to override the Checkout.prototype.back() method. I did not test it but we could write something like :

   Checkout.prototype.back = Checkout.prototype.back.wrap(function(parentMethod) {

    if (this.loadWaiting) return;
   
    if(this.currentStep == 'shipping_method'){
        this.changeSection('opc-billing');
    }
    else{
       parentMethod();
    }
   

   });

Hope it helps.

When you click on the back button in the onepage steps, you are calling a js prototype method Checkout.prototype.back() (see skin/frontend/base/default/js/opcheckout.js:245).

So, one way to modify the actual behaviour is to override this method :

1. If not already done, copy in your theme the file app/design/frontend/base/default/template/checkout/onepage.phtml. Then, after the line

   getSkinUrl('js/opcheckout.js') ?>">

Add the following line to add your own js file (that we will create soon) :

<script type="text/javascript" src="<?php echo $this->getSkinUrl('js/opcheckout-override.js') ?>"></script>

2. In your theme, create the file skin/frontend/<your-theme>/default/js/opcheckout-override.js.

3. In this file, we have to override the Checkout.prototype.back() method. I did not test it but we could write something like :

   Checkout.prototype.back = Checkout.prototype.back.wrap(function(parentMethod) {

    if (this.loadWaiting) return;
   
    if(this.currentStep == 'shipping_method'){
        this.changeSection('opc-billing');
    }
    else{
       parentMethod();
    }
   

   });

Hope it helps.

When you click on the back button in the onepage steps, you are calling a js prototype method Checkout.prototype.back() (see skin/frontend/base/default/js/opcheckout.js:245).

So, one way to modify the actual behaviour is to override this method :

1. If not already done, copy in your theme the file app/design/frontend/base-or-rwd/default/template/checkout/onepage.phtml. Then, after the line

   getSkinUrl('js/opcheckout.js') ?>">

Add the following line to add your own js file (that we will create soon) :

<script type="text/javascript" src="<?php echo $this->getSkinUrl('js/opcheckout-override.js') ?>"></script>

2. In your theme, create the file skin/frontend/<your-theme>/default/js/opcheckout-override.js.

3. In this file, we have to override the Checkout.prototype.back() method. I did not test it but we could write something like :

   Checkout.prototype.back = Checkout.prototype.back.wrap(function(parentMethod) {

    if (this.loadWaiting) return;
   
    if(this.currentStep == 'shipping_method'){
        this.changeSection('opc-billing');
    }
    else{
       parentMethod();
    }
   

   });

Hope it helps.