Webi 4.0 - Prompts - Runtime сalculation default values. Is it possible?

BI 4.0 SP6

I want to set default date values in prompts - between from and to.

Values must be calculated. Formulas:

1. Date From = CurrentDate - 7 days

2. Date To = CurrentDate + 7 days

It's very popular requirements from report users.

In other BI tools (non-sap), it's no problem with it. But not in Webi...

I can't find the way to do this in Webi.... Only manual static values.... In Crystal for enterprise - you can (using interactive Filters - and using formulas on default values).

Is it possible in Webi somehow or not ?