Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal
hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any)
As Long
Public Const CB_FINDSTRING = &H14C
Private Sub Combo1_Change()
Dim iStart As Integer
Dim sString As String
Static iLeftOff As Integer
iStart = 1
iStart = Combo1.SelStart
If iLeftOff <> 0 Then
Combo1.SelStart = iLeftOff
iStart = iLeftOff
End If
sString = CStr(Left(Combo1.Text, iStart))
Combo1.ListIndex = SendMessage(Combo1.hwnd,B_FINDSTRING, -1, ByVal CStr(
Left( ombo1.Text, iStart))
 
If Combo1.ListIndex = -1 Then
iLeftOff = Len(sString)
Combo1.Text = sString
End If
Combo1.SelStart = iStart
iLeftOff = 0
End Sub

Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal _
hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) _
As Long
Private Const CB_FINDSTRING = &H14C

Private Sub Combo1_Change()
Dim iStart As Integer
Dim sString As String
Static iLeftOff As Integer
iStart = 1
iStart = Combo1.SelStart
If iLeftOff <> 0 Then
Combo1.SelStart = iLeftOff
iStart = iLeftOff
End If
sString = CStr(Left(Combo1.Text, iStart))
Combo1.ListIndex = SendMessage(Combo1.hwnd, B_FINDSTRING, -1, ByVal CStr( _
Left(ombo1.Text, iStart)))

 
If Combo1.ListIndex = -1 Then
iLeftOff = Len(sString)
Combo1.Text = sString
End If
Combo1.SelStart = iStart
iLeftOff = 0
End Sub

1、一条语句要分二行或多行，在分行的末尾加一个空格 + 一个英文下划线，不然程序按多行语句处理，二产生错误。
2、Public Const CB_FINDSTRING = &H14C 定义 Const 的关键字不是 Public 而是 Private
3、Combo1.ListIndex = SendMessage(Combo1.hwnd,B_FINDSTRING, -1, ByVal CStr( _
Left( ombo1.Text, iStart)) 语句少一个 ) 号。
给你修改的语句的语法应该没有错误了。

谢谢