Yep,

This example (in C#) inserts data from the taskpane (a selected table
row) into the InfoPath document:

1) Create this function in your FormCode.cs file:

public void InsertLoanSchedule(double TotalMonthlyPay,  double
TotalLoanAd)
{
//Add your code here to update xml nodes in xDocument
}

2) In your taskpane htm file add the following function (in the script
tag):

function InsertLoanData(objLoan)
{

window.external.Window.XDocument.Extension.InsertLoanSchedule(objLoan.TotalMonthlyPay,
objLoan.TotalLoanAd);
}

3) Call the function from your html item (eg table row) - a double
click event in this example:

<tr id="item6" TotalLoanAd="3500.00"  TotalMonthlyPay="169.7"
AnnualRate="15" onDblClick="InsertLoanData(this)">
<td unselectable="on" width="109">3500.00</td>
<td unselectable="on" width="412">169.7</td>
</tr>

Voila!!