InfoPath Dev

I have a list in sharepoint with two fields: WorkCode, Description

I have a form in sharepoint with a repeating section. In the repeating section I have a dropdown (WorkCodeDescription)that lists WorkCode. I want to populate another text box (WorkCodeNumber) in my form with the corresponding WorkCode from my sharepoint list when Description is selected from the drop down.

If I do a filter data on WorkCodeNumber like this:
@Code[WorkCodeDescription = @Description]

When the form is run, only the workcode from the first repeating item is used or can be changed.

I have also tried to make a Rule on WorkCodeDescription dropdown that sets the WorkCodeNumber, the form behavior is the same.

Is this impossible?

I think the other way this could be done is by having just one field in the list i am lookup up in sharepount that concat both WorkCode and Description together.

Then in the form I tell the text boxes to truncate the appropriate peice off for whichever text box I am populating.

So for WorkCodeNumber I would truncate the Desciption off the front.

Any ideas how I can do that?

Here is my xpath

xdXDocument:GetDOM("work codes")/dfs:myFields/dfs:dataFields/dfs:work_codes/@Code[xdXDocument:get-DOM()/my:TimeSheetInfo/my:group1/my:group2/my:WorkCodeDescription = ../@Description]

I am very sorry I have found what I need from this page:

http://www.infopathdev.com/howto/tutorials/default.aspx?i=9111ef580f95479890fc18fb2c5bac85

Many many thanks to everyone.