Example of setting a value of a related item in an onBeforeDelete event in Aras Innovator

setValueOnDelete.cs

Innovator inn = this.getInnovator();

// Get the relationship with the related_id
Item rel = inn.newItem(this.getType(), "get");
rel.setID(this.getID());
rel.setAttribute("select","related_id");
rel = rel.apply();

// Make the change to the related item
Item related = inn.newItem("Part", "edit");
related.setID(rel.getProperty("related_id"));
related.setProperty("name", "NEW_VAL"); // <-- Set the value of your linked property here.
related = related.apply();

if (related.isError())
{
    return related;
}

return this;