I've write some piece of code, that allows to easily create a custom char.
It's written in MASM32 (only 6kB

here's the prototype:
CustomCharDlg (HINSTANCE hInst, char *pBuff)
The first parameter is a instance handler, passed to a dialog box and the second is a buffer for output string (generated CustomChar code).
The passed buffer address MUST pointing to a string which is at least 39 bytes long. The function displays a dialog, where a CustomChar can be easily drawn, then if user click 'Insert' the passed buffer is filled with a customchar code, otherwise if user closes the dialogbox or click Cancel the zero is written to the first byte of buffer.

It would be very nice is someone implements it in Smartie

Of course i can provide a source code of this DLL if there is such need.
The DLL and a simple demo application which use the DLL is at:
http://tresjazz.pl/customchar.zip
The demo app is holding the buffer for string and just calls the dll's function, after that it shows the result string in a MessageBox.
regards