for (i = 0; i < global.inv[global.invid, 1]; i += 1){
        for (j = 0; j < global.inv[global.invid, 2]; j += 1){    
            if (get_mouse(global.inv[global.invid, 3]+i*40, global.inv[global.invid, 4]+j*40, global.inv[global.invid, 3]+i*40+39, global.inv[global.invid, 4]+j*40+39)){
                global.inv_selected = i+(j*global.inv[i, 2]);
            }else{
                global.inv_selected = -1;
            }
        }
    }