Unrelated custom field

I apologize for so many posts. The answer to this, im sure, is pretty simple. I need to insert the data from a custom field of a different product.

I know how to insert a custom field from the current product: <?php echo $this->row->custom_field; ?>

But I need to do (otherproduct)->row->custom_field; somehow. I realize i need to call upon the data, so it will be a bit more complicated.

Thanks for your help,
Carey