How can I set the init file and plugin as a relative path

[lazycatme]

Hi,
when change the firefox profile name or move it to another path, I have to reset those two path.
I have try to create a fold in \extensions\[email protected]\content\keysnail,
and set
user_pref("extensions.keysnail.userscript.location", "chrome://userchromejs/content/keysnail");
user_pref("extensions.keysnail.plugin.location", "chrome://userchromejs/content/keysnail/plugins");
but it can't work.How can I set the relative path? Thanks you!