run time error 52

I was running an application for checking parameters in excel file when the messege showed " run time error 52". Please help how to solve this. below is the area where i encountered this problem.


Private Sub CommandFormat_Click()
Dim FileSize As Long

totalcount

If CheckBox1 = True Then
FileNumber4 = 2
Open "C:\IOlistErrors.txt" For Append As FileNumber4 "--------------------------- the problem was highlighted in this command line"
Print #FileNumber4, ""
Print #FileNumber4, "<< FILE CHECKED: '" & Workbooks(DAiowb).name & "' >> " & DateTime.Date & " " & DateTime.Time
Print #FileNumber4, ""
Print #FileNumber4, ""
Print #FileNumber4, ""
Close #FileNumber4