ExpandEnvStrings

Hi
I am a newbe in the world of NSIS.

Can anybody show me a working exampel of using the
ExpandEnvStrings command

I want to do something like

ExpandEnvStrings $1 COMPUTERNAME
WriteINIStr "c:\winnt\dss.ini" "Common" "InterComIP" $1

That is i want to write the computername in an ini file

ReadEnvStr $1 envvar

or

ExpandEnvStrings $1 "%envvar%%yetanotherenvvar%"