How can I reset instfiles page?

Good time of day. Sorry if my English so bad.
I wrote NSIS script for installing some MSI (MicroSoft Installer) files. I can't decompile it, because files have signature.
All files required serial numbers for installing.
script:

!include "nsDialogs.nsh"

....

!include "MUI2.nsh"

....

Page Custom GetSN

!insertmacro MUI_PAGE_INSTFILES

...

Var HWNDGetSN

Function GetSN

	nsDialogs::Create 1018

	Pop $HWNDGetSN

 ... ; fields for SerialNumbers

	nsDialogs::Show

FunctionEnd

...

Section ... ; install section

 ExecWait 'MsiExec /i "1.msi" PIDKEY=$SN1' $0

 StrCmp $0 "1603" is1603 ; check return code. 

is1603:  ... ; How i can return to GetSN page? And after correct SN retry Install files. 

 ExecWait 'MsiExec /i "2.msi" PIDKEY=$SN2' $0

 ... ; check return code. How i can return to GetSN page? 

 ExecWait 'MsiExec /i "3.msi" PIDKEY=$SN3' $0

 ... ; check return code. How i can return to GetSN page? 

SectionEnd

I can return, using that method http://nsis.sourceforge.net/Go_to_a_NSIS_page
but if I push Install button again... NSIS script don't clear status for installfiles page.

I think if you jump to the end of the last section to allow the installer to leave the InstFiles page before going back to your custom page; that should sort it.

Stu

oh.. Big thanks.
Really, when i return to SN page after Instfiles page it's work correctly. I do it using another custom page.
script:

!include LogicLib.nsh

!include "nsDialogs.nsh"

....

!include "MUI2.nsh"

....

Page Custom GetSN

!insertmacro MUI_PAGE_INSTFILES

Page Custom verifyInstall

!insertmacro MUI_PAGE_FINISH

...

Var HWNDGetSN

Function GetSN

	nsDialogs::Create 1018

	Pop $HWNDGetSN

 ... ; fields for SerialNumbers

	nsDialogs::Show

FunctionEnd

...

Section ... ; install section

${If} $InstallStatus == "true" 

 ExecWait 'MsiExec /i "1.msi" PIDKEY=$SN1' $0

 StrCmp $0 "1603" is1603 ; check return code. 

is1603: 

 StrCpy $InstallStatus "false"

${EndIf}

${If} $InstallStatus == "true" 

 ExecWait 'MsiExec /i "2.msi" PIDKEY=$SN2' $0

 ... ; check return code. 

${EndIf}

 ... ; other files

SectionEnd

Section -FinishSection 

  ${If} $InstallStatus == "true"

; wrilte links and unstaller

  ${EndIf}

SectionEnd

Function verifyInstall ; функция для создания страницы проверки. 

  ${If} $InstallStatus == "false"

    StrCpy $R9 -3

    Call RelGotoPage

  ${EndIf}

FunctionEnd

After that I have only one question: Can I disable "Back" button on finish page?

GetDlgItem $R0 $HWNDPARENT 3
EnableWindow $R0 0

Use in a defined MUI_PAGE_CUSTOMFUNCTION_SHOW function for your finish page.

Stu

Thanks a lot. script working correctly now