ScreenMix() - combine a string of charcaters with string of colours
 Mixes characters and colours of a screen
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 Syntax

     ScreenMix(<cChar>, <cAttrString>, [<nRow>], [<nCol>]) -->cNull

 Arguments

     <cChar> is the a string of charcters to use.

     <cAttrString> is which colour strings  to mix with the characters in the
     <cChar>.

     <nRow> is the starting row at which the resulting string is to be
     displayed. The default is the cursor line.

     <nCol> is the starting column at which the resulting string will be
     displayed.  The default is the cursor column.

 Returns

     ScreenMix() always returns a null string, or "".

 Description

     ScreenMix() may be used to combine a plain character string with a
     string of colour atributes to create a screen image which can then be
     displayed to the active window.

     ScreenMix() applies the first colour attribute, <cAttrString>, to the
     first <cChar> and so on.

     <nRow) and <nCol> are used to determine where the resulting screen
     should be displayed from.

 Notes

     ■  This function does not alter the cursor position.

 Examples

     ■  The folowing charceters are used to represene the basic strings:

        cChar: = "1Help"
        cAttrString: = CHR(116) + REPLICATE(CHR(113), 5)

     ■  Show output at the current cursor position:

        ScreenMix(cChar, cAttrString)

     ■  Show output at line 24 at the cursor column:

        ScreenMix(cChar, cAttrString, 24)

     ■  Show output at line 0, column 0 of the active window:

        ScreenMix(cChar, cAttrString, 0, 0)

 Files:  Library is MRWINDOW.LIB.