How to read runtime Macro in Wix -

i want read name file or read command line after creating installer file.

i have defined macro in mainproject.wxs file as

< ?define product = "xyz"?>

and reading macro "product" follows,

< registry action="write"

              id="registryentryid"               name="installdir"               key="software\$(var.product)\myownname"               root="hklm"               type="string"               value="[installpath]"               keypath="yes"/> 

on build time.

but want define , read "product" on runtime after installer created, can change product name according file content on runtime, suggestions helpful.

thanks in advance.

a macro handled preprocessor. request variable can changed @ runtime. need use property.

<property id="projectname">xyz</property> 

this property can changed @ runtime.

you read property this:

[projectname] 

there different ways of changing property. in custom action.