Multi-select in drop down?

Really love the plug-in. I have what I think might be a feature request, but I’m not sure if it’s possible today.

I am using this to make a search with a dropdown that contains values from a custom field. As it is set up today, I can only pick one value in that drop down at a time.

Is there any way to set this up so that I can pick multiple values in the dropdown at once?

Thanks!

http://ww.wp.xz.cn/plugins/wp-custom-fields-search/