Doesn't Recognize/Find Rectangle

[Paige]

Am using the following code in a worksheet module (to attach an object to the
cell when it is active); however, it comes back with a message that says
"item with the specified name wasn't found". I don't know why this is
happening, as I can see the item on the worksheet itself and the name is
correct (Rectangle 87). Moreoever, I have exactly the same code in the
module for another sheet in this workbook, but with different rectangle
names, and they work fine. Any ideas on what is going on here?

Option Explicit
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim Box87 As Shape
Set Box87 = Me.Shapes("Rectangle 87")

If Not (Intersect(Target, Range("M2:M50")) Is Nothing) Then
With Target
Shapes("Rectangle 87").Visible = True
If Selection.Left + Selection.Width + Box87.Width > Rows(1).Width Then
Box87.Left = Selection.Left - Box87.Width
Else: Box87.Left = Selection.Left + Selection.Width
End If
If Selection.Top + Selection.Height + Box87.Height >
Columns(1).Height Then
Box87.Top = Selection.Top - Box87.Height
Else: Box87.Top = Selection.Top + Selection.Height
End If
Box87.ZOrder msoBringToFront
End With
Else: Shapes("Rectangle 87").Visible = False
End If
End Sub