on parameters

Hi,
I have 3 parameters-
columnname -takes the column name like name, course, marks
operator - takes the operator - <.>.<= value - takes the value like 30,computers , english etc
i want to pass these parameter to a table and filter the value out.
how can i make the operator as a parameter ?
in the filter expression -
i can give in the column name - column parameter
value - value parameter
but how do i give the operator ?
Thanks
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