how to verify a directory?

I use installoptions to create a custom page
add a dirrequest control,I want to verify the value that user input ,if it is not a directory,user can not continue

how can i do it?thanks

StrCmp $R0 "" +2

IfFileExists "$R0\*.*" +3

 MessageBox MB_OK|MB_ICONSTOP "Bad path!"

 Abort

Assuming $R0 is the path read from the INI file.

-Stu

good idea,thanks ,fantasy