Match whitespace except a specific line that itself contain a whitespace

I have this example:

ED Ess  Nb  Ip

I would like to capture all whitespaces except the two present between "Ess" and "Nb".

ED·Ess  Nb··Ip

Where · indicate what should be captured.

I have try:

(?<!Ess\s)\s+

But it does not work since the Negative Lookbehind itself contains what should be captured.

Do you have a solution ?

>Solution :

Seems like you have to use both negative lookbehind and lookahead to check if Ess or Nb is nearby.

/(?<!Ess)\s(?!Nb)/gm

Here is test

P.S. I might notice that there is an edge case where the regexp would capture whitespaces if there are more than two present between Ess and Nb.