How to alter the position of block in sidebar

Question

I want to change the position of block in my category pages. I tried in some xml file but couldn't get success.

Any idea would be appreciated.

Answer 1

I guess thats the correct answer for Kishor

<block type="cms/block" name="BLOCK_1" before="-"> 
    <action method="setBlockId"><block_id>BLOCK_1</block_id></action> 
</block> 
<block type="cms/block" name="BLOCK_2" after="BLOCK_1"> 
    <action method="setBlockId"><block_id>BLOCK_1</block_id></action> 
</block> 
<block type="cms/block" name="BLOCK_3" after="BLOCK_2">
     <action method="setBlockId"><block_id>customer-rev</block_id></action> 
</block>