newbie needing help

right ive created a form with an edit box that i want them to fill in as a date of birth, and once the box is filled in the program automatically calculates the persons age, now ive placed a limit on the edit box but i want to know how do i get it to auto calculate the age once the limit is reached, because i dont want to place a button in that the user has to press to calculate the age of the person each time

The following code will calculate the users age for you.

procedure TForm1.Edit1Exit(Sender: TObject);
var
BirthDay : TDate;
Age : Variant;
S : String;
X : Integer;
begin
BirthDay := StrToDate(Edit1.Text); {Entered Birthday}
Age := Date - BirthDay; {Todays Date - Birthday = No of days Old}
S := Age / 365.25; {Divide days old by days in a year}
X := Pos('.',S); {Locate any decimal point in the result}
if X > 0 then Delete(S,X,100); {If decimal point exists delete the characters after it}
Label1.Caption := S; {Assign Age to label1}
end;

As for not wanting to have to press a button, I placed this code into the edit boxes onexit event so that when the user tabs out of the edit box their age is displayed. You could probably adapt this code witha Try Except statement and place it into the onChange event but I didnt try that.