dropdown and datepicker question

I have two tables in database MFBANK (contains names of banks) and MFBRANCH (contains all branches of all banks listed in MFBANK). In the grid, colBank represents MFBaNK and colBranch represents MFBRANCH.

1. How do I make so that colBranch lists only branches of whatever selected bank in colBank of the same row?
2. How do you insert datepicker in the grid?
3. MFBANK has bank code, so when I choose certain bank from the grid, I want the grid to display the bank name, but when saving data to server, I want the bank code to be saved instead of the bank name. Is this the default behavior?
4. When populating grid from data sent from server, I arrange the sql syntax so that the resultset contains bank name and bank code. I want bank name to be displayed, but I also want the bank code to be recorded as well, so when I save the grid again, it still knows the bank code. How do I do this?
5. I have a case where I want to check if the content of certain cell is a number or not. If the user types in non numeric char or pastes an invalid number format, I want the cell to revert back to its old value. Do you provide an event for this, so I just need to code like:
function afterChange(oldValue, currentValue){
if isNaN(currentValue) currentValue=oldValue;
}

If you have these features, there's a very big chance I'll buy this product. Thanks