InfoPath Dev

(preface: I am an experienced .net developer and bangning my head against the wall with this)

 InfoPath Feature Needed: to populate a textbox that show the current software version based on the ProductNumer (list column value) and the Module Type (unique column names) after the user selects each value from a two drop down boxes. (very simple in asp.net)

I have a Sharepoint list with these columns:
   * Product Number (PK in SQL)
   * Multiple Columns that define the module types

I then have a primary fields list that has simply Modules as a list:
Module:
mod1
mod2,
mod3 

example:

ProdNo, mod1, mod2, mod3
 beta       1.1      1.5      1.3
  ver1      2          2         2.5

I have a form our tech will fill out that have two drop down boxes:
ProdNo: (prodNo list)
Module Type: (Module Columns)

 with a textbox Module Update (to version No)

What I need is once they have selected the Prod No and the Module Type the text box will return the version number that module is at, so selecting:
  ProdNo: Ver1, Module Type: mod3
--will update the textbox to:
 2.5

I have tried the instructions using the cascading drop down boxes example and honestly the instructions are vague and perhaps missing some steps. Anyways, I can not get anything to work and I have tried every varation.

In the Module Type drop down I run the rule:
 Set Field Value; and I select Command from the data connection QdabaraRules
 For the Value: I set the filter: concat("FilterOwssvr/dsname=FilterOwssvr/filter=Mod2 /value=", ProdNo)   (I hard coded the filter to a specific column so I can get some results, I want this to eventually come from the selected dropDown Module Type)
 I then set the drop down to the FilterOwssvr for the data source and selected a XML row column.

I can not get it to autopopulate. What I really need is the Module Update textbox to update the version number based
the ProdNo & ModuleType. How do I achieve this? The only thing I have been successful with is populating the secondary drop down box that is suppose to be driven by the selection of the first drop down box if I set the check box to retrieve data at form load for the XML connection, which is not scalable, I need it query on the selection of the module type drp down.

Can your filter rule actually accomplish what I am trying to do or do I need to write my own web service?

It looks like you're missing the required spaces before the forward slashes.  When all else fails, check the value of the Error field, as that will help track down a large number of issues.

It also looks like your command is trying to locate list items where the Mod2 field is equal to the value of the ProdNo field in your form.  If I understand your explanation above, ProdNo, Mod1,2, and 3 are all separate columns, no?