I got this to work using thes code below for the buton.

Apparently, the SharePoint data is accessed in the same name space as the
InfoPath data, i.e. ../infopath/2003/dataFormSolution or "xhtml:dfs"

I still need to do two things.

One, I need to blank the target table before I start writing values to it.  
As it is now, everytime I click, the selected values are appended to what
could be a partially filled out list.

Two, I need to be able to filter the SharePoint source.  Our Software
profiles support life cycle and I only want titles with the "current" value
equal to true.

Thanks for helping!

here's the code.

function CTRL14_5::OnClick(eventObj)
{

//Get a reference to the Table1 data connection
var objTable1DOM = XDocument.GetDOM("SoftwareProfiles");

   
//Set the SelectionNamespaces property of the Table1 data connection to walk
the DOM
objTable1DOM.setProperty("SelectionNamespaces",    
'xmlns:dfs="http://schemas.microsoft.com/office/infopath/2003/dataFormSolution" ' +
'xmlns:xd="http://schemas.microsoft.com/office/infopath/2003"');
     
//Get the selected items
var objSelectedItems =
objTable1DOM.selectNodes("//dfs:myFields/dfs:dataFields/dfs:SoftwareProfiles[@Selected = 'true']");
     
//Loop through the selected items
    for(i=0;i<=objSelectedItems.length -1;i++)
{
//See if the first record in the destination Repeating Table is blank
if(XDocument.DOM.selectSingleNode("//my:group12/my:group13/my:field46").text
== "")
{XDocument.DOM.selectSingleNode("//my:group12/my:group13/my:field46").text =
objSelectedItems(i).attributes(0).text;
}
else
{
//Add a new row   
XDocument.View.ExecuteAction("xCollection::insert", "group13_20");
//Get a reference to that new row
var objNewItem =
XDocument.DOM.selectSingleNode("//my:group12/my:group13[last()]/my:field46");
//Set the text of the field
objNewItem.text = objSelectedItems(i).attributes(0).text;
}
}
}