There are a couple of ways you could do this, I think:
1. Make the root source for both the LC database and the company database the same LDAP system. Then both products would be effectively using the same data. This may not be possibe for you.
2. Develop an SPI that obtains user information from your custom database, rather than from the usual LDAP.
You can find API info here:
You will find some sample code for building an SPI in the samples directory of your LiveCycle installation.
When you configure a directory in adminui, there is a checkbox to indicate that it uses a custom SPI.
Howard
http://www.avoka.com