The VBA program with NI-VISA 4.6.2 can run ok , but will get the error(NI_NULL display constant expression required) when run in another computer with verion NI-VISA 5.2 .The VBA program have loaded the visa32.dll . Would you advise what is the difference between two version of NI-VISA .I need to use NI-VISA 5.2 , would you advise what i should do next step . Thanks!