Limit Characters

Try pasting this into the ThisWorkbook tab

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
Application.EnableEvents = False
Dim Cell As Range
Set MyRange = Range(Sh.Range("A1"), Sh.Range("A7"))
For Each Cell In Target
    If Intersect(MyRange, Cell) Is Nothing = False Then
        Cell = Left(Cell, 7)
    End If
Next Cell
Application.EnableEvents = True
End Sub

I've made some additional improvements to cope with entries into more than one cell.