Qurey for approval

Hi

I wish to introduce an approval for A/R Invoice  and it should  be when a certain condition meets,

The requirement is:

Based on the Whse and the doucment total i need approval for adding the A/R invoice

Example :    when i create a A/R Invoice in which Delhi is the Warehouse, and document total is >=3 lakhs, i need approval

i need this form at for all the whse's,,

any one could get me the query for this approval,,,,

Regards