Can anyone please tell me why this Voucher Date is not updat

Question

My VBCoding here

Tally.Vouchers.UpdateVoucher.VoucherDate = txtDate.text (Date is = 01/01/2013

 
My Problem is when I check Voucher date in Tally it is : 01/04/2012

Can anyone please tell me why this Voucher Date is not update??

Thanks in Advance