Can we extract data from one module if we are on a other separate module

HI Team,

I want to know if we can extract data from another module to a separate module, lets say I have one module :event which has attachments as a child, now i have another custom object which stores some information on attachment types in list. so my aim is to check what is the attachment type and then fill some values in event or attachment module, the checking should be done from the custom object.

Thanks

Manas