To highlight the fields in the text you can use this code:
VB
WPDLLInt1.SpecialTextAttr(wpInsertpoints).Hidden = True
C#
WPDLLInt1.SpecialTextAttr(SpecialTextSel.wpInsertpoints).Hidden = true;
To make the merged text use a gray background use this code
WPDLLInt1.SpecialTextAttr(wpAutomaticText).BackgroundColor = &HE0E0E0 ' gray
Memo.ShowFields = true
In this mode the field names are displayed in boxes and the merged text is hidden: 