Script Extension conversion to Button click script

[Giovanni_Briggs]

An extension of Airtable’s Currency Conversion script: Airtable Scripting

Rather than assuming what currency you want to convert to, this script pulls in the list of all known conversions into its own table (using USD as the base currency). You can then create links to this table to pull out the corresponding currency conversion rate. Re-running the script updates the conversion rate, which then propagates to all linked records and calculations.

Base in Universe at Currency Conversion Import Script - Airtable Universe

[Matthew_Rogers]

I would like some help evolving this script to have variable base currencies. If we assume 3 columns as follows:
1) Base currency (Dropdown from: usd, gbp, eur, aed etc)
2) Value (number)
3) Converted to desired currency (currency)

so each could be entered in any currency and then converted to the desired currency.