field dependency

Am trying to create Field dependency for Us states relative to respective time zones for lead object.Like whenever create a lead ,have to choose the Country and if its US country , then have to select the States and the respective Time Zone will autopopulate automatically.

But in Field dependency I have selected the Respective Time Zones for Respective Us states,but its showing the Error as : Select at least one cell from the table below.

Please Help

Any help would be Appreciable.

if anybody have any other idea how to execute,that's also appreciable

Thanks in Advance!!