Dave,
I did this 2 years ago and after several hundred hours of work found out that isntantiating about more than 200 or so containers of appts brought the form to a crawl.
So I bought DBI Tech's controls only to find they still have several bugs after 2 years and make them totally unreliable for use in the 'Real World'.
Writing controls in Delphi gives a very fast compact control, which also isn't reliant upon the MFC42.DLL, etc. files. The controls work fine and ALWAYS fire my events as opposed to DBI's ctDays control. However, I don't like the fact that VFP shows the ActiveForm to be my OLECONTROL because of a lot of menus that I use the SKIP clause with looks at the ActiveForm.
Now I am changing some of the OLEMISC status bits to see if that helps but so far no luck.