set column width

i'm using java to write the xl/worksheets/sheet1.xml then open it to *.xslx. I'm having problem setting column width. I don't know the syntax or how. Can anyone help me please? Here is my xl/worksheets/sheet1.xml code:
Thanks.

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Site/Lane


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Event Timestamp (Eastern Time)


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LSC Pkg ID


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Officer Corrected State


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Officer Corrected Plate


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LPR State


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LPR Plate


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Corrected Action


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Officer Decision



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L247 / 02


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12/18/2009 12:02:14


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0000000000000000f2df0d010000c85f


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NM


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KSL247


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A



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I am not an expert, but I have tried the modifing the cols node , which is just before the sheetData .

for example
<worksheet .... >
......
  <cols>
    <col min="1" max="4" width="18.85546875" customWidth="1" />
    <col min="5" max="5" width="18.85546875" style="5" customWidth="1" />
    <col min="6" max="6" width="18.85546875" customWidth="1" />
  </cols>
 <sheetData>
.......

the width attribute is measured in "number of characters" , which I found no definitive definition.
min and max are just column index (one based).