Filter Collection input results

I was wondering, can I make a related content item filter based on the related item above?

Here is the related part of my main item entry:

<perch:related id="brand_slug" collection="Brands" label="Brand Slug" required="true">
    <p><perch:content id="slug" type="slug" /></p>  
</perch:related>
<perch:related id="group_slug" collection="Group" label="Group Slug" required="true">
    <p><perch:content id="slug" type="slug" /></p>  
</perch:related>

Ideally I want 'Group_Slug' to only show items that have the same 'Brand_Slug' as what I have selected above. Is that doable or just madness?