How to get one object from a string in OTBI Reports

Hi Team,

We have a requirement where would like to get a particular object from a string which has _ in it.

Example:

This the string we have in one column

Evaluation_OLC383056_ILT Feedback Survey_Advance facilitation Skills

Now we would like to fetch the object which starts with "OLC" and the entire number.

here our new column should give us the value "OLC383056"

Here we tried Substring function but this number is not fixed characters one, in some cases it has 8 characters in some cases it has 10 characters.

Considering all this how can we achieve this in OTBI reports