Need to replace particular content in a xml file

Hi,
My requirement is to find a text and replace it with another in a XML file.
I am new to Unix,Please provide some suggestion to achieve.

Find:

<Style ss:ID="ColumnHeader1">

Replace with:

 <Style ss:ID="ColumnHeader1">
  <Borders>
    <Border ss:Position="Bottom" ss:LineStyle="Continuous"ss:Weight="1"/>
    <Border ss:Position="Top" ss:LineStyle="Continuous" ss:Weight="1"/>
  </Borders>

Thanks In Advance

sed '/ColumnHeader1.*/ { i\
<Borders>
<Border ss:Position="Bottom" ss:LineStyle="Continuous"ss:Weight="1"/>
<Border ss:Position="Top" ss:LineStyle="Continuous" ss:Weight="1"/>
</Borders>
}'
val='<Borders>\n<Border ss:Position="Bottom" ss:LineStyle="Continuous"ss:Weight="1"/>\n<Border ss:Position="Top"
 ss:LineStyle="Continuous" ss:Weight="1"/>\n</Borders>'

sed '/<Style ss:ID="ColumnHeader1">/ a '"$val"' ' infile

To make the changes inline, use -i option

sed -i '/<Style ss:ID="ColumnHeader1">/ a '"$val"' ' infile

--ahamed

Hi Ahamed,
I am getting the below error while executing your solution.

sed: Function /<Style ss:ID="ColumnHeader1">/ a <Borders>\n<Border ss:Position="Bottom" ss:LineStyle="Continuous"ss:Weight="1"/>\n<Border ss:Position="Top" cannot be parsed.

Can you look into this?

You should use the "$val" in sed. Did you do that? And moreover it should be one single line literally separated by \n.

--ahamed