How can one build charts with formula fields only in Crystal Reports

Hi,

I tried to see how this can be done, but if I create a new report and a couple of formula fields, the insert chart stays greyed out. I see on this link that it should not http://msdn2.microsoft.com/en-us/library/ms227622.aspx.

Anyone know what it wrong??

It should be simple enough as this link claims.

Thanks.

Regards,

Mike