Search Meta data\custom fields

Hi there,
I have a wordpress install running the event calendar, and i have used the custom fields to aid in the maintenance, organisation etc. of events.

my calendar is set up here https://www.moshmonkey.com/calendar

now what i want to do is add a drop down menu of the different keys, city, venue etc. and an input box so people can search each custom field and then for it to only list the events with that meta data. just like it does with the listing of each month\day etc.

im sure this is possible, and won’t be to difficult but i just can’t seem to get my head around writing a plugin\hack like this from scratch.

Anyone think they can help, or at least point me in the right direction.

Thanks

Ben