Create a conditional format using the set_num_format()method, this enables you to distinguish between different cells values by assigning color backgrounds. I heard a lot of Monks mention things about WIN32::OLE module, I believe it has to be a strong one, so better try it out and learn it, I would want to learn it too....SpreadSheet::WriteExcel has some disadvantages I was not aware of until I have tried doing stuff and then crashing on the discovery that this module could not well do it satisfactorily or even not do it at all...here is a link to some more examples on SpreadSheet::WriteExcel that you might find useful http://www.koders.com/perl/fid2656ED1AA9FDA418F78129684CD3956AA785DC9D.aspx

$f_change->set_num_format('[color 10]0.00%; [Red]-0.00%;[Orange]0.0%')
+;
$worksheet->write(3,3,0,$f_change);
$worksheet->write(2,3,-0.015,$f_change);
worksheet->write(1,3,0.085,$f_change);
[download]

using this set_num_format can allow you to give colors to positive percentage ranges, negative percentage ranges and zero...I have been there before, so this code, extracted from a program I wrote does not have bugs in it.