I don't think you can!
/home/export/user1 $ sqlplus /
> @script1.sql
> HOST CD /home/export/user2
> @script2.sql
script2.sql has to be in /home/export/user1
.
You either use the full path, or exit the script and start sqlplus
again from the right directory.
#!/bin/bash
oraenv .
cd /home/export/user1
sqlplus / @script1.sql
cd /home/export/user2
sqlplus / @script2.sql
(something like that - doing this from memory!)