Yes
"Puma tech" makes a program called Intellisync
http://www.pumatech.com/Intellisync_Palm_CE.html

It allows you to to get data from any Palm app.
and lets you choose which fields to save and a date range.
Fantastic product.  I got it for my wife cause she does here time sheet in her Palm VII and I created an Access database to uplink the Calendar.dat file to it and print it out.

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Are there any PC utilities for converting .mdb files to another format .dat for my palm applications ?  

I think Intellisync is not what you want, because you want to covert a file, not sync.
I don't know any app that can transform the .dat file in a csv, but if you want to integrate the file to your own soft I'd recommend to open the datebook Conduit sample (that comes free in the CDK in www.palmos.com/dev ) where the file is created and look at the logic that it uses to create it and invert it to read it.
Still if you want to sync I recommend the Extended systems product (XTND Connect Server) it is easier to use and more powerful.