select with subquery in select clause

Hi I need to make a select from 2 tables whit this layout always with the
newest datetime exchange currency.
The local cuurency is Mexican Pesos

Table 1 Currencies example:
CurrencyID Key Description
1 USD USA Dollar
2 EUR European Euro
3 Yen Japan Yen


Tabla 2 is Day exchange Currency
CurrencyID Equivalent DateTime
1 12.50 2010-08-07 08:00:00
1 12.55 2010-08-07 08:10:00
1 12.49 2010-08-07 08:20:00
1 12.60 2010-08-07 08:30:00
1 12.51 2010-08-07 08:40:00
1 12.52 2010-08-07 08:50:00
1 12.48 2010-08-07 09:00:00
1 12.61 2010-08-07 09:10:00 <-- the newest xchange for USD
2 16.87 2010-08-07 08:00:00
2 16.90 2010-08-07 08:10:00
2 16.88 2010-08-07 08:20:00
2 16.85 2010-08-07 08:30:00
2 16.87 2010-08-07 08:40:00
2 16.92 2010-08-07 08:50:00
2 16.80 2010-08-07 09:00:00
2 16.95 2010-08-07 09:10:00 <-- the newest xchange for Euro
3 6.73 2010-08-07 08:00:00
3 6.70 2010-08-07 08:10:00
3 6.78 2010-08-07 08:20:00
3 6.75 2010-08-07 08:30:00
3 6.77 2010-08-07 08:40:00
3 6.72 2010-08-07 08:50:00
3 6.70 2010-08-07 09:00:00
3 6.75 2010-08-07 09:10:00 <-- the newest xchange for Euro

The select query I need is always the newest exchange currency for each
currency in table 1, something like this

CurrencyID Key Description Equivalent DateTime
1 USD USA Dollar 12.61 2010-08-07 09:10:00
2 EUR European Euro 16.95 2010-08-07 09:10:00
3 Yen Japan Yen 6.75 2010-08-07 09:10:00

How can i do the select?

Plese help me
Jose Roberto Chavez