For a registration tool we always created the case ID by the following line of code.
Me.RMA_Nr = Format$(Now(), "yymm") & Format$(Val(Right$(DLast("[RMA-Nr]", "TBL_RMA_ISSUE"), 3)) + 1, "000")
unfortunatly we get now always the same issue number where should I look where this is going wrong. this line worked for over a year.