BPM form mapped to drop down "none selected" workaround

So I learned all kinds of cool things to screw up at insights. One of them that looks particularly handy is this BPM form. So I am playing around with that today. One of the bugs that they pointed out during the classes was this “none selected” thing that shows up when you map an NVChar field to a drop down on the form. But they didn’t show a very good workaround. You can get it to select when you click on the down arrow on the drop down and it finds what’s supposed to be in there, and then you’re good (that’s what they showed). But that defeats the purpose of the pre-filled BPM form if they have to go to it and click on it, especially if it’s buried in the tabs or if the error message isn’t great.

Does anyone have a workaround to get the system to do the validation for the field upon completion of the BPM? Running the trace when clicking on the field I see the ChangeUOMClassID method fire, which must be what I need to fire to do this validation. Is there a way to trigger this Method to fire at the end of my post processing directive? I suppose I need some custom code for that. Any help would be great. See screen shots below for an example of what I am talking about. We are on 10.0.700 if this makes a difference.

<tracePacket>
  <businessObject>Erp.Proxy.BO.PartImpl</businessObject>
  <methodName>ChangeUOMClassID</methodName>
  <returnType>System.Void</returnType>

So I started trying some stuff.

I saw this post in the forum:

Which gets me to a coding guide. I found on page 10 for calling BO’s from custom code. Here’s my BPM so far

I added the assembly that I think I need.

I added the using statement, but this is probably wrong.

Then I added the code, this is obviously wrong. The example from the help has a lot more, but I don’t know what any of it means, and it just says “add the necessary code”, and I can’t google that so I’m stuck…

I’m pretty sure that I am just past my coding ability with this one, but if someone has an easy fix I would love the help.