RegEx Help Needed (find some text)

I have a txt file that contain something like this:

blablabla

blablabla

blablabla

Lock files:

blablabla

blablabla

blablabla

blablabla

!!autoit~~

//AUTOITaaa

--autoIT//aaa

blablabla

blablbla

blablba

</pre>

blablabla

blablabla

AUTOIT

I would like to count home many word "AUTOIT" (case insensitive) between word "Lock files:" (case insensitive) until first </pre>

(on example above, it's 3>

How can I do that?

Thanks