Hi Stephen,
Thanks for your interest in Syncfusion Products.
If you would like to append the percentage sign with the value entered in cell, it can be achieved by setting FormattedText property of GridStyleInfo object in PrepareViewStyleInfo event. Here is the code for your reference.
if (e.ColIndex == 5)
{
e.Style.FormattedText = e.Style.Text + "%";
}
Here is a minimal sample in which this has been implemented in gridcontrol.
http://files.syncfusion.com/support/samples/Grid.Windows/7.3.0.20/F89280.zipRegards,
Rajadurai