NSIS silent installation vs2013 runtime

; install VC Environmental Science
Function InstallVC
   Push $R0
   ClearErrors
   ReadRegDword $R0 HKLM "SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{20C1086D-C843-36B1-B678-990089D1BD44}" "Version" 

   ; Detection contains vc Whether the registry information of exists
   IfErrors 0 VSRedistInstalled
   Exec "$INSTDIRvcredist_x86.exe /q"   ; If it does not exist , Perform a silent installation
   StrCpy $R0 "-1" 
   ; MessageBox MB_OK  $R0 

VSRedistInstalled:
   ; MessageBox MB_OK  " already installed " 
   Exch $R0
 ; Delete "$INSTDIRvcredist_x86." 
FunctionEnd