problems with bound date fields with null value

hi all,

just recently encounter this problem.. in my form, i had a couple of textboxes bound to a datetime type column.

the problem is that i can't leave the textbox null if i already placed a value in it before. the cursor will not leave the item until i enter a valid value.

my date field can accept null values so i want to allow users to not enter a value for this textbox...

also, i don't like to use the DateTimePicker control just in case anyone suggests that.

another question is that is it possible for a textbox to display an invisible value? i thought of using a date like 12/31/9999 for null values but it should not display it on the textbox.text property.. anyways, this is what i'm thinking as a last resort.

i'd appreciate any help..

thanks.