Metamagnetic shape memory alloys Ni-Mn-X (X= In, Sn, Sb) undergo martensitic transformation (MT) from a ferromagnetic austenite cubic phase to a low magnetization martensite, accompanied by a large magnetization drop. The possibility of inducing the MT for moderate values of applied magnetic field opens new possibilities for magnetic shape memory effect and for applications like magnetoresistivity and magnetocaloric effect. Co addition not only increases the ferromagnetic coupling of austenite but also weakens the magnetic interactions of martensite, consequently improving the interesting properties of these alloys. We propose a comparative study between ternary Ni-Mn-In and quaternary Ni-Mn-In-Co alloys in transforming and non-transforming compositions to study the influence of Co substitution on the magnetic coupling in the cubic phase and on the magnetic and crystallographic structure of the martensite.