Forms Data Controls :: Enabling And Disabling Gridview Rows?

I have a gridview with Templatefields checkbox, equipname,rate1,rate2 ,rate3,rate4.The equipname name field is a dropdownlist templaefield and I am populating it with data from datatable.

The equipname are A,B,C,D.

When I check the checkbox the corresponding equipname field of the checked row will be active and I select a equipname from the dropdownlist.

Rate1 is for Equipname 'A'
Rate2 is for Equipname 'B'
Rate3 is for equipname 'C'
Rate4 is for equipname 'D'

Now what I need is when I check the first row and select equipname 'A' only the
rate1 column of the first row should be active.

When I check the secondrow and selected equipname only the rate1 column of the second row should be active
and that of row1 should be inactive and so on.

I was able to do everything except that when I check a particular row and selected equipname 'A' allother fields (ie,rate2,rate3,rate4 ) becomes inactive but all otherrows of rate1 irrespective of the checked row becomes also active.how can I do this

I s there any way for getting that particular checked rowindex so as to compare it with