PRINT INVOICE button to dissapear after one print. HOW?

Hello all!

I've made a shop using opencart, i've modified it a little... a little more... but there is someting i wanna do and i don't know how...


(1)


1st of all i will make a new user-type in admin section so that a number of users can only work with invoices (print them, modify them)

Here is the problem: I would like that when someone prints an invoice, the | PRINT-INVOICE |-button to dissapear so that no one can print the same invoice once again, BUT only me as administrator can do it.



(2)



I have a TVA tax (Tax on product price, it rises the price with 24%)... i would like to make a new column in the invoice so that costumer can see the ammount of tax for each product.
Thank you.
I dont need it only for TVA but in general: how to show the tax ammount in invoice-print

exemple: price with no tax= 23
tax-tva=24%
price+tva=28.52 from which TAX-TVA is 5.52 <---- this ammount i need to print in the invoice...

HOW?



Please help me, i know this is not so hard but belive me that i have no idea how to make this. Thank you!

Exactly the same problem for me. Have you found the solution to it?