I have a gridview that is binded to a stored proc. I highlight the rows depending on the result. So after displaying the result, I loop through the rows and highlight those that meet the critera

here's the code for highlighting:
private void HLightRows()
totaltime = timespan.parse(gdView.Rows[i].Cells[2].Text));
if(totaltime.totalseconds >= 1800){
gdView.BackColor = Color.Red;


it highlights fine, but the problem is when I set the gridview AllowPaging = true, after I click on the second page the highlight is gone as well as when I go back to the first page.
I tried putting the HLightRow function to PageIndexChanged and PageIndexChanging Event but still it won't highlight the rows.