Display total discount amount in checkout / auto apply coupon code PS1.7

[Mikeey]

Hi,
I have a customer group that has 30% discount on everything.

Is there a simple way to display the total discount value in checkout page? Maybe some built-in variable that holds the value to add in cart-detailed-totals.tpl..?
I've tried to add a custom variable that counts the discounted value for each product without success. 

Also tried with a custom module that adds a global variable with hookActionFrontControllerSetVariables(), but the value I set there seems to be fixed(?), showing the set value of 0 all the time.

Alternative option would be if there is a way to activate an coupon code automatically upon checkout? This would actually be better since the shopper will see regular prices and then just a 30% discount code upon checkout... 

Thanks in advance! 

/Mike

[Mikeey]

Decided to use voucher and modify the theme a little.. If someone knows a way to activate a certain voucher by default, please get back to me!