How to validate dynamically generated text box

[TheFuzzball]

Okay, here is the problem:
I have two text boxes, DOB (Date of Birth) and Age.
Age is not gotten from the table, instead it uses this formula in the Control Source: "=DateDiff("yyyy",[DOB],Date())" in order to calculate the age in years.
This works beautifully, except I need to validate the Age box using "<=14 And >=19" but this validation is ignored because the information is generated dynamically.

Can anyone please suggest a way of making this work, or possibly another way of approaching the problem.

I don't have very much experience with Access, so please be gentle

[TheFuzzball]

I used this formula: <=(DateAdd("yyyy",-14,Date())) And >=(DateAdd("yyyy",-19,Date())) to validate the date in the DOB cell directly.