i try to get a selected text and the word under mouse in firefox

after a lot of search i get the solution that i must access a document's HTML in Firefox using IAccessible

i found that solution in c++ in this link How to access a document's HTML in Firefox using IAccessible

the solution use ISimpleDOMNode.idl file so the first step to convert that solution from c++ to c# is convert

ISimpleDOMNode.idl to tlb file and convert tlb to dll fill

i try to use VS Command Prompt with this command to convert to tlb file midl ISimpleDOMNode.idl

but That generate ISimpleDOMNode.h and ISimpleDOMDocument.h, which define the interfaces. It also create ISimpleDOMNode_i.c and ISimpleDOMDocument_i.c but there is no tlb file

what is the wrong ?