GridView And DropDownList In Each Row

Question

I've created gridview in which there is 4 dropdown in each row......

.........

Now i want if user select 1st dropdown value from 1st row then 2nd dropdown should be enable in same row..

 ..

& when user select 2nd dropdown value from 2nd row then 2nd dropdown should be enable in same row

....... 

I wrote event of

ddlPlatform_selectedIndexChanged

on dropdown

.....

but the problem is that when I select value from 1st dropdown from 1st row then it enables 2nd dropdown of same row......

which is correct.........

.but......

if i select value from 2nd dropdown from 2nd row then it enable 2nd dropdown of

.............."1ST ROW AGAIN" it should be on 2nd row not in 1st

.........

its becuase the index of row is not changing on

ddlPlatform_selectedIndexChanged

Its hard to understand but please anyone help.

Thanks to read and in advance.