I use Coinmarketcap API to update my excel spreadsheet.
Maybe this a solution for you also.
The API can be found here
https://api.coinmarketcap.com/v1/ticker/bitcoin/https://api.coinmarketcap.com/v1/ticker/ethereum/and so on.
There is an easy way to import it to excel.
Just click the Data tab
Look for Get Data > Other Sources > From Web
And paste the API address.
Then everytime I want to update it, I just click Data > Refresh All
I think it will work for your OpenCalc software, but the names might be slightly different.