TessEngineMBS.SetRectangle(Left as Integer, Top as Integer, Width as Integer, Height as Integer)

Call after SetImage.
Each SetRectangle clears the recogntion results so multiple rectangles can be recognized with the same image.

TessEngineMBS.SetVariable(Name as String, Value as String)

Dim OCR As TessEngineMBS // your instance of tesseract

OCR.SetVariable("tessedit_char_blacklist", "xyz")

Supply the name of the parameter and the value as a string, just as you would in a config file.
Returns false if the name lookup failed.
e.g.
SetVariable("tessedit_char_blacklist", "xyz") to ignore x, y and z.
Or
SetVariable("classify_bln_numeric_mode", "1") to set numeric-only mode.

SetVariable may be used before Init, but settings will revert to defaults on End().

Note: Must be called after Initialize(). Only works for non-init variables (init variables should be passed to Initialize()).