Why can't Office Word display properly my font?

Fonts and More General Font Discussions
1

Here are the four letters I added into my font. They’re displayed perfectly in Notepad.
Untitled.jpg
I mapped them in the Private Use Area, at 4 first codepoints (E000->E003). Then I added this script

feature liga
 script latn;
lookupflag IgnoreMarks RightToLeft;
    sub V acutecomb by uniE000;
    sub v acutecomb by uniE001;
    sub uni01EA acutecomb by uniE003;
    sub uni01EB acutecomb by uniE002;
} liga;

But when I used the font with Office Word, they showed up like this: All combining acute accents are gone.

Has anyone had this kind of problem? Does anyone know what this is about?
Here’s the font:
Untitled.jpg

2

It works just fine on my Windows 7 with Microsoft Office Word 2007.