In A1 the conversion rate, assume it is based on what one dollar is in Euros
(0.744139 rate for today), in B1 the amount in dollars, in C1

=A1*B1

if you have what one Euro is in dollars (1.34393 rate for today) in A1 then
use

=B1/A1

hi
this is usually based on exchange rate which changes often. you would have
to have up to date exchange rates from an outside source.
http://moneycentral.msn.com/investor/market/exchangerates.aspx
if $ were in column A then
=A1*exchange rate.
you could put the daily exchange rate in a cell.. say...R5?
=A1*$R$5   copy down
current exchange rate is .74380 Euros per US$.
A1 = $1000.00
using formula above
=1000.00*.74380= 743.80 Euros

Regards
FSt1