LoadFromFile([in] BSTR FileName, [out, retval] long * Value );

Loads picture of custom theme from .BMP or .JPG file. A size of the progress bar control is adjusted automatically to the size of custom loaded bitmap. If height of the bitmap is odd then it sets TransparentColor=true and TransparentColorValue property to the color of the left-bottom pixel of a loaded bitmap.

Returns: error code. A list of error codes:

0: Ok, loaded successfully;
1: Wrong file extention (not .bmp or .jpg);
2: The file FileName does not exist;
3: File reading error.