Frozen Unbound ComboBox on Form, (Leo)

Hi there,
I tried to put an unbound comboBox on my form to use it as filtering option
tool for "Year", from which user can choose desired year from a limited years
and based on that the data on the form filtered for the chosen year.
I followed the wizard of making combobox, and chose the option two, "I will
type the values..." , but this combobox is realy frozen as if it is locked,
while it is neither locked or disabled! I mean it doesn not change the value
by dropdown or typing on it.
For you infor I did not want to use the option three of the combo wizard, as
I need to use my combo box value in another expression for filtering , not
directly the year itself.
now Why is that so? Did I do something wrong?
How can I fix it?
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Thans & Best regards
Leo, InfoSeeker