How to Edit perticular node in XML

How to edit Perticular XML node ?

<root>

<node1>

<data1>dsfs </data1>

<data2>dsfs </data2>

<data3>dsfs </data3>

<data4>dsfs </data4>

</node1>

</root>

What should i do to change data3 value, means edit data of <data3> ?

help me

[371 byte] By [Ghanshyama] at [2007-10-3 4:46:56]