求助：通过变量调用窗体，代码已完成，出现新问题

Dim i As Integer
Dim tmpForm As Form
Dim strFormName As String
strFormName = "frmBack"
For i = 0 To Forms.Count - 1
If Forms(i).Name = strFormName Then
Set tmpForm = Forms(i)
Exit For
End If
Next
If tmpForm Is Nothing Then
Set tmpForm = Forms.Add(strFormName)
End If
tmpForm.Label1.Caption = "Forms集合调用测试"
frmBack.Label1.Caption = "窗体名称直接调用测试"
这段代码执行之后出现两个frmBack窗体，

请赐教问题产生原因及解决办法