[Dfu-util] DFU-util runtime vs DFU mode

I am running DFU-util -d with my vid and pid for my device as parameters. The response is that the device is in runtime mode. When I use the update utility supplied by the chip manufacturer, the device programs and restarts (as per code in the bootloader) I cannot change the USB enumeration details at this point since too many devices have been deployed with existing bootloader code. How can I “fake out” DFU-util to accept a Vid/pid match and run the update? Please advise Bruce Doan