How to Extract Text that doesn't has a fixed length of characthers using Text/ Conditional F.

Summary:

Using EPM Management Report

I see this options for Mid Text Functions:

Left/Right/Mid

Left, Right, and Mid allow you to trim text from the results of other text functions such as MemberAlias and MemberName to keep only the left-most, right-most, or center text.

Syntax
Left (text, [number_of_characters])
Right (text, [number_of_characters])
Mid (text,start_position, [number_of_characters])
Note:
"number_of_characters" is optional for the Mid function.

These are my Aliases examples:

Company 123435325, LLC
Company 123435, LLC
Company 15325, LLC
Company 123435325000, LLC

And I need this:
123435325
123435
15325
123435325000

Maybe something like:
Mid(MemberAlias("Entity"),#, )

However, this only gives me the start position. I need a specific number of characters that stops at ", LLC," similar to a calculated variable. as the num of characters It will vary from alias to alias.