Sure it is!
Well it is not possible using Calculated Column so this will be my first blog about XSL-Rendering inside User Defined Table.
Prepare your module
Insert a new UserDefinedTable module to your page. Add two new columns Debit and Credit with type Integer (or Currency or Decimal...) to the table:

Enter some sample data:

XML Representation of the Table Data
The XML data representation contains the actual data, the fields definitions and context information. Data is stored inside memory as dataset with three tables "Data", "Fields" and "Context". The dataset will be transferred as XML via DataSet.GetXml().
Example: account.xml, main extract:
Writing a XSL-Stylesheet
Open a new file Account.Xsl in your favorite editor.
First we have to define the xsl declaration and an output option which will omit the output of a xml declaration like :

Note the definition of the DotNetNuke/UserDefinedTable namespace. As the xml data is declared with this namespace we need to add an abbreviation for it. Every element inside the xml data must now be accessed with the prefix udt:.
Next we define the main template. It is defined for the root of the input document:

We will loop through all the rows inside the Data table using <xsl:for-each>:

Each row inside the Data table is rendered as one html table row:

<xsl:value-of> extracts the value of a selected node. If it is not present (=null) it will output an empty string.
<xsl:value-of> can also extract the value of xpath expressions. Luckily there is a xpath sum functions which calculates the sum over the given node set. Inside this example the nodeset consists of the current node (.) and all siblings before the current node (preceding-silbing) of the data type (::udt:Data) [Xpath axes]:

Finally we have to close all open tags:

This stylesheet above is very basic.
The extended stylesheet account.xsl provides permisson aware edit links, alternate row colors and conditional formatting.
Publish and select your Stylesheet
Open Manage User Defined Table of your module again. Jump to the Display settings and switch the rendering method to User Defined XSL Transformation. Upload your stylesheet.

Now the module is ready to work.
