Develop a special HTML feature for an EKM Powershop Online Store

I want to sell harp strings online. A particular model of harp has, for example, 34 strings. The customer must be able to select any number of strings, from 1 string up to 34 different strings, from a simple list of 34 strings ... and then be able to drop all those string into their basket simultaneously. You could look at an example of this working at ... [login to view URL] The online shop would list many different models of harp ... and each harp would have a similar list of between 27 & 39 strings. HTML would be required to create this special feature for an EKM Powershop online store.