Error While Running VBA

Please post your VBA code, and tells us on which line the error is occurring (if you hit "Debug", it usually highlights the offending line).

Sub CHECK_STAAD_RESULTS()
Application.ScreenUpdating = False

Dim start_time, end_time
start_time = Now()

Dim xlApp As Excel.Application
Dim xlWB As Excel.Workbook
Dim STAADFileName As String
Dim objOpenSTAAD As Output
Set objOpenSTAAD = CreateObject("OpenSTAAD.Output.1")
STAADFileName = Sheet1.Range("B5").Value
objOpenSTAAD.SelectSTAADFile STAADFileName

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Dim pnResult As Integer
objOpenSTAAD.AreResultsAvailable STAADFileName, pnResult
Sheet1.Range("B15") = pnResult
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
objOpenSTAAD.CloseSTAADFile
Set objOpenSTAAD = Nothing
Set xlWB = Nothing
Set xlApp = Nothing
'Application.ScreenUpdating = True

end_time = Now()
Sheet8.Range("B10").Value = DateDiff("s", start_time, end_time)


End Sub

It looks like this variable is setting your file name:
So what exactly is in range B5 on sheet1?
Maybe you have some characters which you cannot use in file names.

B5 contains:

C:\Users\Arastu\Desktop\RAFT DESIGN CHECK STAAD FILES\ONE LC.std

That seems to look OK.

Are you using some special VBA references, libraries, or add-ins? I think you must be, because I get errors when I try to compile your code in Excel VBA.

yes i am using ref.

OPENSTAAD 1.0 Type Library.

I do not see that as an option in my list.
I take it this might be a reference you pruchased/installed?
If so, I am afraid that I cannot test it out, so I do not have access to it.

yes i installed a software STAAD PRO 2007 in my PC. it is a software for analysis of buildings.

My VBA code check whether the analysis has been performed or not.

if pnResult value = 1 then it means that the analysis performed
and if pnResult value = 0 then it means that the analysis is not performed.

I am afraid there is not going to be much I can do for you, since I do not have that program.

I would recommend stepping through your code one line at a time (using the F8 key). You can then what it is doing at each step, and if you hover over your variables in your VBA code as you pass that line, it will show you what their values are. That might give you some clue as to where the problem is occurring.