Write all of the spots out into a dgn file. Then using dtm tools go to extract graphics. Set file open to create and feature to spots. At the bottom left hand corner of this box click on the box under extract. You can set it to view, fence, or complex chain whichever you decide to use as a boundary for your .dat file. Draw your boundary hit the reset button and then the match button and click on the spots and click apply.
then go to dtm tools build and convert your newly create .dat file to a .tin file.
Then dtm tools load and select your new tin file and click on the general contours feature below. Click read at the bottom right of the box to establish minimum and maximum contours bounds and load for view only to check data.