Yearly MVAT Refund

I am talking bout MVAT

I purchase in VAT and sale in CST due to which in the year 2009 - 10 I have VAT Refund....  in the 1st Half of 09 - 10 I had to pay VAT but in the 2nd half i have a good amount of refund to Claim......... I file 6 monthly returns. 

Now the matter is worst since the VAT has changed from 4% - 5% increasing my Refund claim by 1% monthly...

IN the current year as I see the trend Ill have to claim refund in both the returns i file...  As i understand I have to file form 501 for the claim @ the end of the year..

Is there a way that I can file for refund earlier?? i.e. if I file quaterly return can i file the form 501 along with the return every quater??? so that my refund is expidited???  

OR it does not work that way??? means I HAVE TO WAIT  for the year end to claim my refund???

Would be v. glad if someone could help me out in this...