Input fields - update input box from another input

[wigglesby]

Hi

 

I have 2 input fields:

 

<input type='text'  name='txtitemsremaining".$recId."' id='txtitemsremaining".$recId."' class='teenyinput numbers' value='' />
<input type='text' disabled='disabled' id='txtitemsreceived".$recId."' name='txtitemsreceived".$recId."' class='teenyinput numbers' value='".$poItem->items_received."' />

 

The form Is in 3 parts:

 

Remaining (input field)

Received (input field)

Total (outputs the total from the db)

 

What I want to do is:

 

If the total is 6 and received is 0, then remaining needs to say '6'.

If I then type in 3 into remaining, I need it to update the received value to 3.

If then saved, the page should then display remaining as 3, received as 3 and total as 6.

If i then type 0 into remaining, then received should say 6.

 

I just dont know how to do this with javascript and ajax.

 

Thanks