Regex with lookup range

I want to use the index in order to have the position of a character string.
This string is dynamic so I will have to submit it as a regex
I used lookup range but as i said i can’t refer to the string that i’m looking for because it is dynamic


Can you please explain with example, what is the input string & what is the target output?

For example here:
I have to look for the position of “18-Jul” for each line
So I want to loop through each line to see where “18-Jul” is.
I thought of using lookup range whereas lookup range needs to have a determined string whereas I need a regular expression