how i can insert formula in crystal report by vb.net

hi

how i can insert formula in crystal report by vb.net??

i add new formula in crystal report by vb.net this code:

" CRReport.FormulaFields.Add("test name", "currentdate") "

when open report i see new formula in list for formulas

i want to insert in report by vb.net

how i can ?

use vb.net 2005 , cr 10

use craxdrt.dll

thanks