很可能文件不存在,你把代码改为:
If Filesys.FileExists(ProjectPath & "Attachments\平张排单信息.xls") =False Then
MessageBox.show("文件不存在")
Else
MessageBox.show("狐狸爸爸眼花了,文件是存在的")
End If
Dim Book As New XLS.Book(ProjectPath & "Attachments\平张排单信息.xls")
Dim fl As String = ProjectPath & "Reports\平张排单信息.xls"
Book.Build() '生成细节区
Book.Save(fl) '保存工作簿
Dim Proc As New Process '打开工作簿
Proc.File = fl
Proc.Start()