It depends a bit on how the diagrams are inserted into the document.  That
is, whether they are Shapes or InLineShapes.

But basically, you would use an .Find loop to find the text, then set a
Range to the found text, extend the Range.End to the end of the Range of the
document and then delete the first Shape or InlineShape in that range.  The
code would be something like:

   Dim myrange As Range
   Dim strFind As String
   strFind = "Text to find"
   Selection.HomeKey wdStory
       Selection.Find.ClearFormatting
       With Selection.Find
           Do While .Execute(findText:=strFind, Forward:=True, _
               MatchWildcards:=False, MatchCase:=True, Wrap:=wdFindStop) =
True
               Set myrange = Selection.Range
               myrange.End = ActiveDocument.Range.End
               myrange.ShapeRange(1).Delete
   'or         myrange.InlineShapes(1).delete
               'Now delete the found paragraph
               myrange.Paragraphs(1).Range.Delete
           Loop
       End With
   Next i