Can I use Sass properties as args for my function?

It appears that I’m attempting to use SASS properties as arguments for my function, AND IT’S NOT GOING WELL.

Is there a way in which I can do this, or is there a better alternative to what I’m trying to achieve?

Basically, I want to change the values of variables I send to my function based on my screen width media query.

Currently:

@function myFunc($arg1, $arg2) {
    @debug "arg1 = #{$arg1} / arg2 = #{$arg2}";

    @return #{$arg1} * #{$arg2};
}

.my-class {
    // Mobile first values
    --var1: 10px;
    --var2: 20px;

    @media (--from-tablet-size) {
        --var1: 20px;
        --var2: 40px;
    }

    width: myFunc(--var1, ---var2);
}

The debug output actually shows that the values passed to the function is just the strings --var1 and --var2 rather than their respective property values…

DEBUG: arg1 = --var1 / arg2 = --var2

Is there something that I can do to solve this? Either by passing the properties as I am attempting here, or a better alternative?