[MX04] Check if multiple of given number

[::bluemoth::]

Is there a way for me to check if a value is a multiple of a given number.
Lets say I have 3 columns, and want to make items stack at the end of each 3rd column. How can I go about it without hard-coding it like so? I'm basically wanting to set _x to 0 at the end of every 3rd item, and increase _y accordingly.

        for(){
            if (c == 0 || c == 3 || c == 6 || c == 9 || c == 12){
                rowX = 0;
            } else {
                rowX = ((categorymcwidth + categorymargin) * c);
            }
        }