1. For this You need to place the fields in the details section of the reports where required field value will be shown in the report.
2. Now Click on Detail section and right click and go to properties.
3. In the property window click on Suppress Checkbox Button and then click on the Formula button beside suppress check box and provide the formula within the formula window like
if ((date >='01-01-2001' and date <='31-01-2000') and amount<50) then
return false
else
return true