Re: modifying resource.h and rc files

I downloaded some sample code off of the internet and I am attempting
to add certain features. I am a little confused about how .rc files
work, they have always been autogenerated for me. Here is the code I
have:

m_Control.CreateOffScreenSurface("ChessBoard",IDB_IMAGE);

IDB_IMAGE appears to look up the file name of a picture that the
program is to use. I would like to add a reference to another picture
so that I can display two pictures. The confusing part is IDB_IMAGE
appears to be defined in two places.

The function call is asking for a UINT (where IDB_IMAGE is passed).
IDB_IMAGE is defined as a some form of a constant string as well as a
const UINT. So somehow CreateOffScreenSurface is taking the UINT
version of IDB_IMAGE and looking up the string version. Here is the
two places it is defined:

this is in a .rc file
IDB_IMAGE BITMAP DISCARDABLE "res\\dino600x800.bmp"
[redacted]

What do I need to do to create another variable that points to a
different file? I tried defining a different variable in resource.h
and the rc file, but that didn't work, plus I didn't know what number
to put in the UNIT version.

Can someone help me understand what is going on in these two files?