Wordpress PHP TDO miniforms Geo-plugin

Hi I developing a Wordpress site and have reached the end of my skills. I'm very good at manipulating and understanding code but not so good on the raw writing. Here's my problem:- I've used a hacked TDO miniforms page to insert a client side form into my site. Amongst the options are two to enter a price, one for currency (GBP, US$, Euro), the other the figure. (The currency and figure options are actual custom fields at present, but this is probably not the way forward.) After the client has chosen the currency and input a figure, I want to generate 3 custom field values from those entries via the geoplugin, so I end up with three separate custom fields (GBP, US$, EUR) and their money values (obviously converted at the relevant currency rate via the Geoplugin). Geoplugin also has the ability to generate the local currency, but a drop down menu would be best as then I can restrict the currencies used. Obviously if they choose GBP in the options, it needs to also generate a custom field for GBP as well as the other two currencies. I then need a filtered search sidebar widget/code so I can allow users to search in their own currency. This is a "restricted custom field search" (again probably via a drop down menu). It must operate using from-to values. I.e. the currency code (custom field) is chosen via drop down, and they can search for posts which have prices (custom field values) within a price bracket - for instance say £5 - £10. Any further clarification needed please ask