You can achieve something similar to what you're after by 'slaving' a Table to a PivotTable, with a little VBA. See this answer I posted, that can be adapted to effectively achieve what you want.
Or alternately, you could multiply the individual totals in the source data by a named range called Exchange_Rate, and have a small bit of VBA that refreshes the Pivot whenever that Exchange_Rate input parameter is changed by users.
Here's how that looks:
...and if I change the ExchangeRate variable in that orange input cell:
To do this, I have a small snippet of VBA in the relevant Sheet Module that simply monitors that input cell for any change, and then refreshes the PivotTable so that the Pivot reflects the updated values in the underlying source data:
Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Range("ExchangeRate")) Is Nothing Then ActiveSheet.PivotTables("PivotTable1").PivotCache.Refresh
End Sub
Or you could record a macro while setting up a calculated field at a specific exchange rate, then modify that code so that the rate part gets replaced to match any change to that orange cell:
...and here's the event handler code that does this:
Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Range("ExchangeRate")) Is Nothing Then _
ActiveSheet.PivotTables("PivotTable1").CalculatedFields("Local Cost"). _
StandardFormula = "='Value ($USD)'/ " & Range("ExchangeRate")
End Sub
Or if you have the ability to use PowerPivot, you could use Rob Collie's Disconnected Slicer trick.