[mini]

Dim n, i, timeintvl As Single
移到外邊成為 Form的全域變數
timeintvl As Single 不需要了，因為由 Timer1.Interval取代

==================

timeintvl = pictime * 60 / (i - 1)
改成
Timer1.Interval = pictime * 60 / (i - 1) * 1000 '因為Timer1.Interval是以 ms為單位 1000等於1秒
Timer1.Enabled = True

==================

再把這幾行稍做搬移修改即可
Do Until n = i
n = n + 1
Picture1.Picture = LoadPicture(App.Path + "\圖檔\" & pic(n) & ".jpg")
Call wait(timeintvl)
Loop

>>>>>>

Private Sub Timer1_Timer()

   n = n + 1
   Picture1.Picture = LoadPicture(App.Path + "\圖檔\" & pic(n) & ".jpg")
   if n = i Then Timer1.Enabled = False

End Sub