about Developing dll files

Hi

I have a queation:

For example developing a big project.You divide project to some pieces.And start to writing components.And then coding UI and binding them with your components.

You must install your exe to user cpmputer with your dll files.But how can we restrain that other coders to use our dll's in your application.

I mean for example i installed sygate firewall.In its directory there are some dll's like:
IdsTrafficPipe.dll,Netport.dll,PSSensor.dll etc...

1-)Here how can sygate coded these dll files so they are only using with sygate.exe?

2-)If i develop my application and make dll files to store my methods, how can i avoid to using these dll's other's by binding runtime?

I hope i can explain what i mean.

I am looking for your answers.

It has to do with the search path used to find a dll. Search for the docs on LoadLibrary API call, but usually I think it looks in the current directory (i.e. the .exe install directory) first when trying to find a .dll to load. So if you want it to use only your DLLs, make sure you put them in the same folder as your .exe. Or, I think there is some option where you explicitly specify the folder where it will find .dll files. So you could tell it for instance, that the .dlls are in C:\Program Files\CompanyName\AppName\Libs\. Again, verify this by googling LoadLibrary.