Well, you can compel him to give a valuation but you would have to issue a court application to do that if he will not do it voluntarily. Whether it is worth doing this very much depends on the circumstances and the figures.
There is a very big difference in these two situations:-
1. A company which owns assets, has many employees and is worth millions and
2. A company which is basically a vehicle through which one person sells goods or provides services.
In the latter case it is very unlikely that a spouse would be entitled to a share (save to the extent that there may be a large sum in cash held in the company account which is not needed for any business purpose). That is because such a company is basically the means by which one spouse earns his/her living.
The former case is very different. That is not to say that you are not entitled to the information because you are but it is worth pointing out that there is not necessarily any right to half of a business as there may be be with other assets such as a matrimonial home or pensions.