Order value control in PO after Goods receipt

Dear Gurus,

PO is created against order with value Rs 1 lakh.(Budget Value of order is Rs. 1 lakh) GR also completed and value also booked against order for Rs 1 lakh.

Later PO value was increased to 2 lakh but "budget value exceeded" error message has not appeared and allowed to make LIV for 2 lac.

If GR is not done, the validation for budget value exists and does not allow for more than budget value.

Gurus, Your views please.

Regards,

Kannan.Y.