Excluded Eligible Employees--Same Plan Year

[JWK]

The administrator of a 401(k) plan failed to notify some eligible employees that they were eligible to participate in the plan. We're in the same plan year, but the 3 month de minimis period has expired. We'll notify the excluded employees of their eligibility, but is there a way to fix the period of exclusion before we calculate ADP/ACP at the end of the year? We'd rather clear this up now since these are generally short term employees and will likely be gone by the end of the year. Then we'll have to find them just to give them a very small plan distribution. Any ideas?