I received this question via MSN Messenger from a fellow BLOGer and thought I should post this for others also. If you have a dynamic block where you want your Base Point to ALWAYS be centered with your block, take a look at the attached block.
Example: Say you have a table and you have a stretch parameter on one side of your table. You stretch the block to increase the length of the table. And now you cant get the Base Point to stay centered. Well if you insert a BASE POINT parameter in the MIDPOINT of the table. Then associate a Stretch or Move action with the .50 distance multiplier set. Your BASE POINT will stay centered in your block. Its a nice little way to manage your BASE POINTS for Dynamic blocks.
Check out this block attached to see an example:Download BasePointMid.dwg