Load a product then manually load a custom field:

<mvt:do file="g.Module_Library_DB" name="l.success" value="Product_Load_Code('PRODUCT_CODE', l.settings:product)" />

<mvt:assign name="l.fieldcode" value="'some_code'" />

<mvt:do 
	file="g.Module_Root $ '/modules/util/customfld.mvc'" 
	name="l.success" 
	value="ProductFieldValue_Load_CodeAndProduct(l.fieldcode, l.settings:product:id, l.field, l.settings:data)" />


Custom field value: &mvt:data:value;