Disable next button for unvalid folder names

Hi,

I have to disable next button on the Custom page as well as on the Directory page.

For folders like CON, PRN, COM1, COM2,....,COM9 the next button on the directory page gets disabled but for folder COM0 it does not get disabled though like COM1 we can't create the COM0 folder too.

How can I resolved this issue?
I am using the Windows XP and NSIS 2.24 version.

The test is done by Windows which seems to believe COM0 is a valid filename and even allows you to create files with that name.