Wis. Stat. § 846.14
In case the mortgagor, the mortgagor's heirs, representatives or assigns shall desire to pay a portion of such judgment, taxes, interest and costs, so as to relieve any distinct lot or parcel of the premises which can be sold separately under such judgment from the lien thereof and of such mortgage thereon, the court, on application of such person and on notice to the parties to the action, may, if the amount to be paid therefor is not agreed upon, ascertain and adjudge the proportion of such judgment, taxes, interest and costs to be paid for the purpose aforesaid; and when the amount so adjudged shall be paid as aforesaid it shall relieve such distinct lot or parcel from such judgment and the lien of such mortgage thereon and shall satisfy such judgment to the amount so paid. Any heir, devisee, grantee or assignee of the mortgagor, owning an undivided interest in the mortgaged premises, subject to the lien of the mortgage, may redeem such undivided interest from such judgment and the lien of the mortgage thereon by paying as aforesaid a sum that will bear the same proportion to the whole of such judgment, taxes, costs and interest as the interest proposed to be redeemed bears to the whole of the mortgaged premises.
Wis. Stat. § 846.14