I have to wonder why (in 2024) you are using formfields instead of content controls in your form. Regardless:
Sub FFOnExit()
Dim oFld As Word.FormField
If Selection.FormFields.Count = 1 Then
Set oFld = ActiveDocument.FormFields(Selection.FormFields(1).Name)
ElseIf Selection.FormFields.Count = 0 And Selection.Bookmarks.Count > 0 Then
Set oFld = ActiveDocument.FormFields(Selection.Bookmarks(Selection.Bookmarks.Count).Name)
End If
With oFld
Select Case Len(.Result)
Case Is < 74
.Range.Font.Size = 14
Case 74 To 80
.Range.Font.Size = 13
Case 80 To 90
.Range.Font.Size = 12
Case Is > 90
.Range.Font.Size = 11
End Select
End With
lbl_Exit:
Exit Sub
End Sub