What formula or spreadsheet design should I use to calculate the new interest and principal amounts due after redrawing on a loan half way through the loan period?

eg. 50k loan @ 5%pa payable monthly over 5 years (60 periods), with a redraw of $5k one year in.

I currently use the simple =PMT(Rate,N,-Pv) to calulate monthly repayments over the 5 years of the loan period. I calculate daily interest accrued and subtract that from the monthly payment to give the principal and interest components.

This gives me a daily outstanding balance.

If I then withdraw an amount thereby increasing the outstanding balance, how do I calculate the new monthly repayment? Assuming the term of the loan does not change.

eg. after 12 mths of payments of $943.56 the loan has 48 months left and an outstanding balance of 41,909. I redraw $5,000. What formula do I use to calculate the new monthly repayments?

Thank you!