VB6中APP.path的用法问题

APP.path在使用过程中，总不是很顺畅。经常报错，
如下代码，出现1004错误，无法打开对应的文件。
1、我确定文件位置和程序在一个文件下；
2、我过程检查插入print fullpath，所显示的地址是正确的；
3、我将显示的地址直接提换如下语句中的fullpath
Set xlBook = xlApp.Workbooks.Open("fullpath")
程序也能运行成功。

求大神指点一下迷津

Private Sub Command1_Click()
Dim xlApp As Excel.Application
Dim xlBook As Excel.Workbook
Dim xlsheet As Excel.Worksheet

Dim fullpath As String

If Right(App.Path, 1) = "\" Then
 fullpath = App.Path + "temp.xlsx"
Else
 fullpath = App.Path + "\" + "temp.xlsx"
End If

Print fullpath
Set xlApp = CreateObject("Excel.Application")
Set xlBook = xlApp.Workbooks.Open("fullpath")
xlApp.Visible = True
Set xlsheet = xlBook.Sheets("sheet1")

Text1.Text = xlsheet.Range("A1").Value

xlBook.Close

xlApp.Quit

End Sub

Set xlBook = xlApp.Workbooks.Open("fullpath")
->
Set xlBook = xlApp.Workbooks.Open(fullpath)