Null pointer error while using F4801EditLine

Hi,

I am building a mass upload application to update work order date fields. I have built a headerless application and on row exit of grid have used F4801BeginDoc,F4801EditLine MBF. to validate data at each row and throw any errors like "Requested Date is less than start date" for each row if date is entered wrong. When I copy 500-600 data from excel and paste in grid it throws error as "Null Pointer" This happens randomly and there is no specific time at which it occurs. I copy paste the same set of data from excel and sometimes don't get the