I've written a script which updates an environment variable, but I need to tell Program Manager to update the computer's programs with this new information. I was given this as the API call that is made within another program to cause this:

::SendMessage(::FindWindow("Progman", NULL), WM_WININICHANGE, 0L, (LPARAM)"Environment");

I am attempting to translate this into an AutoHotKey PostMessage call, but I'm doing something wrong, as it isn't working. Here's where I've gotten so far:

PostMessage, 0x1A,, (LPARAM)"Environment", "Program Manager"

Here are the AHK resources I've been looking at to do this:

List of Windows Messages

Send Messages to a Window or Its Controls

PostMessage / SendMessage

And here are the resources that I used to figure out the original API call:

SendMessage function

WM_WININICHANGE message

Can anyone help me figure out what I'm doing wrong?