Natural Account and total amount

Hi,

there is requirement of client that Invoice approval should work on natural account and total amount .

For example

Condition.

if invoice amount 0 to 1,000,000 and natural accounts are 40102 and 40103 then first approver will be different and second and third approval will be same

Natural Account 40102   Approver will be "A" , "B" and "C"      

Natural Account 40103   Approver will be "Z" , "B" and "C"

our requirement is that A and Z will receive first notification and once they approved then B and C receive notification for approval (Only one notification of total Invoice amount). how can cater in EBS ?

Thanks

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