Regex to choose one random occurence of a keyword between a { and } sign -

my text example:

{this text example , keyword, keyword in text multiple times , want 1 of keyword replaced, should chosen randomly every time}

so out of 3 keywords want 1 replaced, chosen randomly. keyword appears more 3 times, once.
possible regex?

no, not possible regex.

you could, however, use regex find of keywords, generate random number, , use number replace 1 occurance.