Problem in Tabindex

I have around 50-60 components and some of the fields are readonly. Now I want to set the tab index only for the fields that are read/write.

Now the problem for me is, some of the components will be added according to the selection in my dropdown list box. Those components that are newly populated also contains some read only text boxes. The thing is, some of the options in the dropdown list may contain or may开发者_JS百科 not contain components.

So how could I Give the tabindex appropriately.

eg : textbox1 : tabindex="1" textbox2 : tabindex="2"

 dropdown : tabindex="3"
            textbox for dropdown : tabindex="?"

 textbox  : tabindex="?"

tabindex values don't have to be contiguous, so you can leave gaps and then when adding your new fields in response to the drop-down selection, you can (partially) fill those gaps.

For instance, let's assume you have three text boxes. You might given them indexes

box1: 10
box2: 20
box3: 30

Then if you add new fields after box2, you might use the indexes 21, 22, 23, etc. New fields after box1 would use 11, 12, 13, etc.