How to Change the Format/Font/Backup of table header of a straight table ?

[#1]

Hi,

I'm trying to change the format / font and the background color of table headers of a straight table in V9 SR2.
I tried the design grid / Custom format cell system but it doesn't work ?? (it works on data but headers stay gray and bold ??).

The only way which seems to be working is to use the (very limited) style sheet. But I'd like to use other things than the pre defined format.

Do you have any idea (see attached file) ?

Best regards