Error in getting parameter as text

Dear sir

When I try to run a python script. I cant get the parameter as text. the following error message is display when it run
This parameter is save from the calender.

Traceback (most recent call last):
File "J:\Gampaha\Scripts\Creating_Building_New.py", line 13, in <module>
VDate = arcpy.GetParameterAsText(4)
File "c:\program files\arcgis\desktop10.1\arcpy\arcpy\__init__.py", line 592, in GetParameterAsText
return gp.getParameterAsText(index)
File "c:\program files\arcgis\desktop10.1\arcpy\arcpy\geoprocessing\_base.py", line 224, in getParameterAsText
self._gp.GetParameterAsText(*gp_fixargs(args, True)))
RuntimeError: Object: Error in getting parameter as text

Thanks

Padmasiri