Not sure if this can be done..

Looking to assign drop down selections a "value" for which, once selected,
can be multiplied by different cells to come up with an extension.

More like assigning a menu of words with a value and then once user selects
that specific item along with another drop down value, an extension appears.

For Example

Tickets to Rome- $590.00 each
Tickets to Paris- $400.00 each
Tickets to New York-$320.00 each

Multiple by:
1 Round Trip Passenger
2 Round Trip Passengers
3 Round Trip Passengers

Equals= Extension.

Possible through Excel?