File error control...?

Hi...

question is ... file overwrite error control.

Section "Test"
SectionIn 2
SetDetailsPrint none
SetOverwrite on
SetOutPath $SYSDIR
File dss.dll
RegDLL $SYSDIR\dss.dll
SectionEnd 

if system had dss.dll and already registered dll.

Installer show File overwrite error.

How to error control?

flag copy file later. then UnReg Old-DLL... Reboot... then copy NewDLL. ... Reg New-DLL


???