Crystal report formulas

hi there, i'm new in VB programming.
currently i'm working on a program that call a crystal report and generate report from a .rpt file
i check my .rpt file is ready and no error
how i define the CrystalReport.Formulas()?
after that, what is the means for CrystalReport.SelectionFormula?
and what is the differents?
cos although i define both formula already
but wen going to the part CrystalReport.action
will having error : 20510:Invalid formula name error.. :sick:
then the report is empty , no data for this selection :cry:
please advice..thanks

Moved to reporting section.

Formulas are part of report
this is a sample formula

Code:

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{factura.preco} + ({factura.preco} * {factura.desconto} / 100)

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Use SelectionFormula when you want to filter the information on the report using sql :

Code:

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{factura.preco} > 100

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Regards
Jorge