Tab indices are same for form items

I have got one outer dynamic form which contains two canvas items.
Each canvas item has got one dynamic form.
When I tab through the entire dynamic form fields, it is not working fine.
I just checked in the firebug and noticed that form items of these 2 canvas items have got same tab index. How to resolve this?
For example : Dynamic Form outer --->CanvasItem1, CanvasItem2.
CanvasItem1 --> dynamicForm df1----> field1--->tabindex-->9231
CanvasItem2--->dynamicForm df2--->field2--->tabindex-->9231

Here above example illustrates two form fields are having same tab indices. How to resolve this?
I don't want to manually set tab indices for these form items?

Please give suggestions....