Thanks for the prompt response, but it hasn't made any difference. I also tried commenting out all the switches below to see if they had any effect but still no event:-
' switches.Add("-dQUIET")
' switches.Add("-dSAFER")
' switches.Add("-dBATCH")
' switches.Add("-dNOPAUSE")
' switches.Add("-dNOPROMPT")