to get filtering work 'Where field' should contain name of list field you want to filter by, not an expression.

the value to filter by should be defined by 'Filtered by control'

filtering, however, works just for equality condition. greater/less conditions are not supported.

to achieve what you need I would suggest to define a view on list that shows just requested future events and then set this view in 'Source view' (above filtering)

Marian, thank you very much. It worked