NGopen()
 Open a Norton Guide database for Acces
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 Function:      NGopen()

 Syntax:        NGopen(cFilename) --> lOpened

 Description:   NGopen() opens a Norton guide for access. This library
                supports one NG file open at a time only. <cFileName> is
                the complete name of the file (including .NG extension).
                Opening the file is a relatively time consuming process,
                as the file has to be checked, and some information must
                be read.

                Be sure not to call any other function of this library
                (except NGlook()/NGdir()) before a succesful call to this
                function, failure to do so will cause unpredictable Errors.

                The guide is opened in Read-Only mode. So there shouldn't
                be any problems on networks.

 Returns:       A logical indicating the success of the Opening.

 Example:       if NGopen('EXPAND.NG')
                     HandleGuide()
                Else
                     Error()
                Endif
                See the supplied DEMO program for more elaborate
                typical usage of the functions (this also applies for
                the other functions).