Deleting records linked to a UDU

Hi

I have developed an SBO 2005 application using a UDO. This UDO has one main table and 3 other tables linked to it.

I have a matrix which is linked to one of these transactions tables. All works well apart from when someone deletes a row from the matrix it deletes all the records including the master record.

Can any anyone suggest how I stop this please ?

Regards Andy