I don't know what an enterget is but this might be what you seek. This puts the integer from each string in its (not "it's") own field. There can be only one instance of ( and of ) in the string. I added sample data for testing purposes.
It looks like this question was posted in the Access forum, but both answers provided are Excel answers.
Are you looking for a strictly calculated field solution, or is it acceptable to create a User Defined Function using VBA. Then you would be able to use that function like any other Access function.