When I use export command at command prompt, it works as expected. But it does not work from shell script.

[root@server shantanu]# export myip=10
[root@server shantanu]# echo $myip
10
[root@server shantanu]# vi myip.sh
#!/bin/sh
export myipadd=10

[root@server shantanu]# sh -xv myip.sh
#!/bin/sh
export myipadd=10
+ export myipadd=10
+ myipadd=10

[root@server shantanu]# echo $myipadd

I want to make the variable available to the same script next time when it runs. In other words I am looking for some way to memorize the variable value.