Can I have 1 to 1 NAT using network ranges?

Hi,

I am trying to create a 1 to 1 nat rule that  will allow traffic to servers xxx.xxx.xxx.6 to 150 to be mapped to zzz.zzz.zzz.6. to 150.

If I try using range objects the rule is rejected - "the data specified is invalid"

My rule is as follows:

Group: No group

Position: 1

For traffic from: Any

Using Service: HTTP

Going to: External Web  (range object)

1:1 NAT mode : Map Destination

Map to: Internal Web ( range object) - I cannot add this to the field.

Any ideas or can't you 1 to 1 NAT with range objects?

Thanks

Jon