UDF for sum of values in different contexts

Hi,

I am getting the source as below and would like to add amount based on the field <a>.

example :

Source Structure:

<Details>

<d>2012-11-01</d>

<a>121</a>

<b>1.1</b>

</Details>

<Details>

<d>2012-11-01</d>

<a>121</a>

<b>2.1</b>

</Details>

<Details>

<d>2012-11-01</d>

<a>122</a>

<b>2.1</b>

</Details>

<Details>

<d>2012-11-01</d>

<a>121</a>

<b>1.1</b>

</Details>

<Details>

<d>2012-11-02</d>

<a>111</a>

<b>9.8</b>

</Details>

<Details>

<d>2012-11-03</d>

<a>121</a>

<b>6.8</b>

</Details>

</Details>

<Details>

<d>2012-11-04</d>

<a>122</a>

<b>5.1</b>

</Details>

Target Structure data:

<Details>

<a>121</a>

<b>11.1</b>

</Details>

<Details>

<a>122</a>

<b>7.1</b>

</Details>

<Details>

<a>111</a>

<b>9.8</b>

</Details>

Here amount has to be added for the respective <a> fields only.

Please let me know for this.

Thank you.