cleanup using custom pattern

Hi all,

I'd like to remove all my company renamed "endregions". So
#region A
// lines of code
#endregion A

will became in:
#region A
// lines of code
#endregion

My idea is to use a custom pattern to find and replace these cases.
But I can't achieve it, I've two problmes:

Problem1: How can I "link" a custom pattern to be found and replaced when doing a code clean up?

Problem2: I've already tried to do the custom pattern and I can't get it.
Knowing that the following regex works correctly to found the pattern: ^(\s)*\#endregion(.+)$
I tried with two identifier placeholders, one for previous possible tabs and spaces and another finding the name I want to remove
$tabs$#endregion$regionName$
where $tabs$ is an identifier placeholder with regex: ^(\s)*
and $regionName$ is an identifier placeholder with regex: (.+)$
Unfortunatelly I can't check if it works because Resharper advise me that $regionName$ is an unexpected placeholder.

Can any one tell me if:
Problem 1 is possible to solve?
Problem 2, where am I wrong?