Gridvalueat function in CR

k i am trying to suppress a field using this line

Code:

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if GridValueAt(CurrentRowIndex, CurrentColumnIndex, 0) > 0 then true

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But i get the error like this: A number, currency amount, boolean, date, time, date-time, or string is expected here.

I am using VS 2008 Professional edition and Crystal Reports basic that comes with it.