Environment variable is a global variable where ever you 
wnat you can use
Defining Environment variable:
Environment("variablename")=34 
Using Environment variable:
msgbox Environment("variablename")

Note:
 
1)it is used when we want value from differnt action
2)it is used when we the value generated in one function is 
used in different function
Ex:
First_Fun a,b

public function First_Fun(a,b)
b=a+b
Environment("c")=b
Second_Fun()
end function

public function Second_Fun()
msgbox Environment("c")
end function

environment variables used  in vb and dis programing we 
will identifies the reausable actions then select/create as 
environment variables in then use that e variable in tool 
wise (on any application)