The QlikView bit should be fairly straightforward, but more importantly you would need to know what your users understood by conversion to dollar, i.e. what FX rate are they expecting to be used?
So if the PO are for separate dates (information not in your request) users may expect conversion at that dates rate, or a month-end rate for the month of transaction, or a current rate (in something that refreshes daily say). Organizations then generally have official sources of rates that they would choose to apply - from Reuters for example.
If you are just trying to do something quick & dirty then you could get sample current FX rates from Google & apply them to each row by joining/ApplyMap & calculating.
