Urgent: restrict textfield events on reaching its maxlength

[Muralidhar]

I've a textfield whose maxlength=1,which takes values as 'Y' and ' '(a
blank space).On

entering some data in this field, onkeypress and onkeydown events are
fired.When the field

already consists of ' '( a blank space) as its value, on again taking
focus into it and

pressing enter or some other key, the above events are fired.I do not
want these events to be invoked if the field consists of ' ' as its
value.How to restrict firing these events when its maxlength is
reached? Can anyone help me out in this matter.

Thanx in advance
Murali