Website Modification

Avg Bid (SGD)
Project Budget (SGD)
$10000 - $30000

Project Description:
I am doing an online store. My concept of the store is to sell items in bundled tied price. For example. pick 10/15/20 items for $18/$26/$32. When user check out with only 9 items(for example), system will prompt user to select another 1 item before allowing them to check out. When user select 13 item (for example), system will prompt them to either select 2 more item or discard 3 items. There is no need to display individual price since the items is to be sold in bundled only. Currently, my product is tag to just one price and I am not able to achieve this effect. Please let me know if you can help. Thanks
Joolma version:2.5.8
Virtuemart version: 2.0.16

Skills required:
Joomla, Virtuemart
About the employer:
Public Clarification Board
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