Adding empty elements for alignment

Hi

I have the following XML structure.

SOURCE:
<table>
        <row1>
                <column seq="1">Value</column>
                <column seq="2">Value</column>
                <column seq="3">Value</column>
                <column seq="4">Value</column>
                <column seq="5">Value</column>
                <column seq="6">Value</column>
        </row1>
        <row2>
                <column seq="1">Value</column>
                <column seq="3">Value</column>
                <column seq="5">Value</column>
        </row2>
</table>

REQUIRED OUTPUT:
<table>
        <row1>
                <column seq="1">Value</column>
                <column seq="2">Value</column>
                <column seq="3">Value</column>
                <column seq="4">Value</column>
                <column seq="5">Value</column>
                <column seq="6">Value</column>
        </row1>
        <row2>
                <column seq="1">Value</column>
                <column seq="2"/>
                <column seq="3">Value</column>
                <column seq="4"/>
                <column seq="5">Value</column>
                <column seq="6"/>
        </row2>
</table>

PROBLEM:
<row1> can contain 1 or many <column> elements.
<row2> can contain zero or many <column> elements. I want to output
empty <column> elements so <row2> columns align with <row1>.

Any help will be greatly appreciated.

--
Kevin Bird