InfoPath Dev

I have created drop down field "STATE" which is populated by an xml data source showing all 50 states, per the following example:

<items>
<item>Arizona</item>
<item>Arkansas</item>
<item>California</item>
</items>

 I would like text box field "GL" to display the related numerical IDs based on the selection in "STATE".  For example, If user chooses California in State, GL value is 382.  If user chooses Washingion, GL value is 145.

 I know I could set the value using rules but not sure how to write the formla.  Any ideas?

You could modify your XML file to include the correct number for each state and use a default value for GL. I've attached a simple sample - save it locally and then you right click the file to open in design mode and preview it. Under Data --> Resource Files you can export the XML (if IP 2007, Tools --> Resource Files) so you can see how I set mine up. Right click the text box on the form and select Properties to see the formula I used for the default value.

I'm only able to get this to work halfway.  In my form, the formula for field name "GL"  is value[name = State].  This is according to your example.  For some reason, it keeps erroring out because "State" is not a filter in the resource file. 

 External datasource has filgers name and value.  the drop down list works perfectly.  in your example, field1 is not in the resource file so not sure why yours works and mine does not.  Any ideas?

Okay, now I've made a little progress.  I was able to resolve the error by editing the xpath

 xdXDocument:GetDOM("STATES")/items/item/value[xdXDocument:GetDOM("STATES")/items/item/name = xdXDocument:get-DOM()/my:myFields/my:State]

Now, the only problem is when I select different states, the GL value stays the same.

You want this:

xdXDocument:GetDOM("STATES")/items/item/value[../name = xdXDocument:get-DOM()/my:myFields/my:State]