Refund of vat

Dear  All,

One of my cleint had Purchased  Scrap Material  From  Kerela.

The Seller had  levied  4 % VAT (kerela state) on tax Invoice and 4%VAT(kerela state)  was paid by Client. 

The Buyer is from Gujarat. 

But In the Tax Invocie with VAT and  no CST was lieved.

Now We Client of Gujarat needs want to  Refund of  excess VAT (kerela state)  by  issuing CST  Form

Is it possible to pay excess  VAT amt  2%  ( VAT 4%  -  CST  2 % C form )

Need  your Suggestion  what  is possible  to  get the REFUND  of VAt  and getting CST paid.

Thanks