Automatic updating a multi-select field from user input single select field

[Dennis Toman]

In the forum, under http://www.reviewsforjoomla.com/forum/index.php?topic=12156.msg50868#msg50868 I asked about how to work around the inability to limit the number of selections in a multi-select field.

 

As indicated there, I think we have a workaround: Let the user input the values into several single select drop down fields, and then have the administrator manually update the multi-select field that is actually searched for the listings (i.e., the single select drop down fields are not used except by the user)

 

I would like to automate this process. I could probably hack something but I would like someone to be able to code this more efficiently/effectively than what I could do on my first try. Anyone comfortable with tackling that, and letting me know what the cost would be? Thanks.