1. 字段A 2010-10-03 09:30:55
   字段B 2010-10-04 05:30:50
24小时制，请问怎样求这两个时间差？
2.如果改成
  字段A 09:30:55
  字段B 13:30:50
请问又怎样求这两个时间差？

Option Explicit

Private Sub Form_Load()
    Dim t1 As Date, t2 As Date
    t1 = "2010-10-03 09:30:55"
    t2 = "2010-10-04 05:30:50"
    Debug.Print t1, t2, CDate(t2 - t1), CDate(t1 - t2)
End Sub

Function GetDoTime(time1, time2)

  secondvalue = DateDiff("s", time1, time2)
  
  dayvalue = DateDiff("d", time1, time2)
  
  hourValue = Fix((secondvalue - dayvalue * 24 * 3600) / 3600)
  
  If hourValue < 0 Then dayvalue = dayvalue - 1: hourValue = 24 + hourValue
  
  minitevalue = Fix((secondvalue - dayvalue * 24 * 3600 - hourValue * 3600) / 60)
  
  If minitevalue < 0 Then hourValue = hourValue - 1: minitevalue = 60 + minitevalue
  
  secondvalue = secondvalue - dayvalue * 24 * 3600 - hourValue * 3600 - minitevalue * 60
  
  If secondvalue < 0 Then minitevalue = minitevalue - 1: secondvalue = 60 + secondvalue
  
If dayvalue > 0 And hourValue >= 0 Or hourValue = -1 Then hourValue = 24 + hourValue
  
  
     GetDoTime = hourValue & ":" & minitevalue & ":" & secondvalue
     
     End Function
此代码能计算不超过2天的时间差,精确到秒值.