jQuery Grid Plugin - jqGrid

let's say in database, I have table MFBANK–> name of banks

and MFBRANCH –> name of branches of all banks listed in MFBANK

1. column ColBank contains data from MFBANK, and ColBranch contains branches of the bank selected in colBank. So values in ColBranch depends on ColBank. How do I do this?

2. When populating ColBranch, I need to first load the all branches from all banks to ColBranch, otherwise ColBranch won't show anything. Is there a way around this?

What I really want is something like jqgrid to provide an event, say like onDropDown event that behaves like this:

function onDropDown(colIndex){

//ColBank which contains bank names is indexed 0, ColBranch is 1

if(colIndex==0) getListOfBankNamesFromMFBANK;

if(colIndex==1) getListFromMFBRANCH_WhoseBankCodeMatchesColBank;

}