PIX Source NAT

Anyone know of a way to take a source block and NAT it to a single IP coming
into the PIX?

Example (arbitrary IPs):
Connection: 207.75.75.0/24 to 10.75.75.75
NAT: 10.20.20.20 to 10.20.20.21

I can NAT the source and destination on a 'per IP' level:
------------------------------
access-list NATtest1 extended permit ip host 207.75.75.35 host 10.75.75.75
access-list test1NAT extended permit ip host 10.20.20.21 host 10.20.20.20
static (outside,inside) 10.20.20.20  access-list NATtest1
static (inside,outside) 10.75.75.75  access-list testNAT
----------------------------------------

I won't get into the reasoning of this (beyond my control)... but just
looking to see if there is a way to NAT the source of a block that is
external to the PIX. I tried using a nat (outside) 30 207.75.75.0
255.255.255.0 and a global (inside) 30 10.20.20.20 but it didn't like the
nat statement (shot back warning) and failed to NAT the source properly.

I know this probably shouldn't be done/needed on the PIX, but due to vendor
issues and political vision, this would be the easiest in the short term if
possible to accomplish.

Thanks for any input
- Ryan