You're "programmers", and you "would want to change it using a function call" but "not modify it" ???
"Changing" and "Modifying" are the same thing. That rude link to the Google Search for "stupid answer" is spot on. LOL
Your title says "programmatically change" i.e change the program ... you say you're "programmers" but you DON"T want to modify it, you only want to know how to use the "backend" ??? This is really making no sense at all.
This is changing and modifying it ... but you say you don't want to modify it. ??? Again ... no sense. And where does it redirect to? It simply refreshes the page when a currency is selected.
You mean ... you're "programmers", but you don't know how to use the Currency Switcher???? I don't really know what you want. You "do want". you "don't want" ???
Honestly ... all your comments and replies make no sense at all I'm afraid. You should just plainly state exactly what you want.
I'll take a guess and presume you want to know how to use the Switcher ... OK?
Just enable it in Alidropship Woo>Settings>Currency, then add the widget from the Appearance>Widgets where ever you like or use the shortcode [adsw_currency_switcher] in your header or in the HTML of theme files.
If that is not what you're asking, I'm sorry ... and I give up trying to make logical sense of your post and reply