Reusable Variables

I’d like to know if there’s a way to store variables in Zoho Analytics that I can use in metrics or calculations. For example, I have a Currencies table that stores the value of different currencies over time. I’d like to use the value of the US dollar (or another currency) to convert other metrics into US dollars and display them in widgets. I understand that unified metrics require table relationships, but I’d prefer not to create artificial relationships between my Currencies table and the other tables. Is there a way to achieve this without establishing those relationships?