A lot depends on the depth of integration that you desire. DB is designed to be a self contained game engine - though there are a lot of ways to get it to communicate with the outside world - and therefore it doesn't easily maintain communication with other independent apps.
Based on your question, I'll assume you know something about programming the windows API, you can pass information from a windows app in the form of a string and start a DBC app using the winapi command:
and in DBC, add the command:
at the top of the code.
I've knocked together a quick example of this process. In the attached zip file, there are 2 programs.
Extract the files to the same directory. Launch start_dbc_app.exe and a dialog box will open up with a text box and an ok button. The text box is just to hint at the idea of entering a password. Whatever you type in this box will be part of what will be sent to DB.
Once you click on OK, what you typed will be stored in a string and then dbc_app.exe will be launched and that string will be passed to the command line variable in DBC called cl$().
It's from cl$() that you would parse out what ever information you want DB to use. In this case you mentioned currency.
The C code, excluding the window creation and control definitions, that does the actual launching looks like this:
// get text from edit box and check for zero length
MessageBox(hwnd,"Length of password must be at least 1 character","WARNING!",
strcat(buffer," and any additional parameters \n attached to string");
MessageBox(hwnd,("%c",buffer),"Text sent to DB",
/* Start the db app by sending a shell execute command */
/* Close the password window */
The full DBC code that gets launched looks like this:
set display mode 800,600,32
sync rate 0
make object cube 1,25
position camera 0,0,-50
text 0,0,"The String received is :"
turn object right 1,.2
Enjoy your day.