Rotation Matrix question

Hi. I found a C function that builds a matrix to rotate one 3D vector to another. Question is, how do i use the resulting matrix? I want to be able to rotate from one vector to another in small increments.

void BuildRotationMatrixFromTo(VECTOR *From, VECTOR *To, XFORM3D *p);

Thank you in advance.

Search quaternion rotation SLERP.

Thanks for the help. Cheers.

Did you ever find a solution to this problem?