InfoPath Dev

I have included a Multiple-Selection List Box in an InfoPath form for a List Library.  If I right click on the control I can see that the "Get choices from an external source" is selected and my external source is showing. 

 

But if I right click on the field in the Fields list, my external choices are gone, and the only option I have it to manually update the choices. Everythign else is greyed out so I can't connect to the external list? I am confused on how to get this to work properly.  In Datasheet View, my external choices are also missing, only leaving me with the manually created options.  My options list is rather lengthy hence the need for it ot pull from the external source (another list in the same library/site collection).

 

Any suggestions? 

 

I think the choices are connected to the control, not the field.... but I could be wrong. Is this a SharePoint list form? Or a 'normal' InfoPath form?

It is a SP List that I altered the InfoPath for.  I think I figured out a solution.  I think Multi-selection boxes are useless in a list library and only useful in a form library.  I ended up using a LOOKUP column and ticked the box allowing multiples selections.  Now my form works as well the data entry from datasheet view works as well.  Crisis averted!  Now if I could get the values to order correctly (added an ordering column to ensure they show up as the client indicated, but the ordering is still off). I will resolve it.  Thank you for your response!