Impromptue formatting issue with excel o/p

[syamku]

Hello,

  have a strange problem with excel formating.. I have one imr. Report with prompt. 
when i run the report and save the o/p in Excel format for the first prompt value
the formating is reflected.from second prompt value the formatting not reflected
in the excel o/p.Colour and font are changing.if i close the session and open again
and run the report the formating comes correct(again for the first prompt value).
It is only with Excel format.pdf is working fine.

Regards,
Syamku