find mid-point irregular part

Not sure about the mid-point, of surface or part, do you mean the centre of rotation or centre of gravity?
Evaluate - Mass Properties will give you centre of mass.
With surface or solid face you can get the section properties (evaluate tab again), good for bending calcs, second moment of area is given along with the centriod - this only works on planar surfaces.

Thanks for your response.
I have an irregular surface and need to find it's center to add another feature onto it, at it's center

If you choose reference geometry and create a point by clicking on the face, the default reference is "center of face" and will place a point at the center of the face.

Hi Rohit,
I have already tried the method which you described. It does find a point on the face, but it is not absolutely in the centre. I have an rregular surface of 5 sides, each side is of a different length. The centre point which is found, is not quite in the centre.
Have you any other ideas? Thanks again for taking the trouble to answer my query.

Sorry for delay in answering..Been out of town. Thanks again for your trouble.