I'm not quite sure of your question, but the corporation doesn't really need to do any withholding for the health insurance it pays for or reimburses you for.
The amount of health insurance is added to box 1 of the W-2, but not any other boxes. Because of that, you could do Federal Income tax withholding, but if you qualify for the Self Employed Health Insurance deduction, that won't be taxable on your personal tax return, so you I wouldn't do any withholding. It is exempt from Social Security and Medicare taxes (FICA).