Skipping pages: Button should say "Install" instead of "Next" - nsis

Question

I have an installer using the Modern UI 2 (MUI 2) that installs up to three components into different locations.
I use a MUI_PAGE_COMPONENTS page and multiple MUI_PAGE_DIRECTORY pages which are skipped automatically if the corresponding section is not selected (like described here).
So far so good.
However, if the last of the three components is not chosen to be installed, the button on the previous (not-skipped) directory page should say Install instead of Next, because next the last directory page will be skipped and the installation will be executed.
Since we already know which page will be skipped after we leave the components page, I wonder if there is a way to make it work?
Minimal example:
!include MUI2.nsh
InstallDir $EXEDIR
OutFile "skip.exe"
RequestExecutionLevel user
ShowInstDetails show
!insertmacro MUI_PAGE_COMPONENTS
!define MUI_PAGE_CUSTOMFUNCTION_PRE directoryPreA
!insertmacro MUI_PAGE_DIRECTORY
!define MUI_PAGE_CUSTOMFUNCTION_PRE directoryPreB
!insertmacro MUI_PAGE_DIRECTORY
!insertmacro MUI_PAGE_INSTFILES
!insertmacro MUI_LANGUAGE "English"
Section "A" SEC_A
DetailPrint "Installing A..."
SectionEnd
Section /o "B" SEC_B
DetailPrint "Installing B..."
SectionEnd
Function directoryPreA
# Skips the directory page for A if not chosen for installation.
${Unless} ${SectionIsSelected} ${SEC_A}
Abort
${EndUnless}
FunctionEnd
Function directoryPreB
# Skips the directory page for B if not chosen for installation.
${Unless} ${SectionIsSelected} ${SEC_B}
Abort
${EndUnless}
FunctionEnd

Answer 1

!include MUI2.nsh
!insertmacro MUI_PAGE_COMPONENTS
!define MUI_DIRECTORYPAGE_TEXT_TOP "Dir:A"
!define MUI_PAGE_CUSTOMFUNCTION_PRE directoryPreA
!insertmacro MUI_PAGE_DIRECTORY
!define MUI_DIRECTORYPAGE_TEXT_TOP "Dir:B"
!define MUI_PAGE_CUSTOMFUNCTION_PRE directoryPreB
!insertmacro MUI_PAGE_DIRECTORY
!insertmacro MUI_PAGE_INSTFILES
!insertmacro MUI_LANGUAGE "English"
Section "A" SEC_A
DetailPrint "Installing A..."
SectionEnd
Section /o "B" SEC_B
DetailPrint "Installing B..."
SectionEnd
Function .onSelChange
GetDlgItem $0 $HWNDPARENT 1
${If} ${SectionIsSelected} ${SEC_A}
${OrIf} ${SectionIsSelected} ${SEC_B}
SendMessage $0 ${WM_SETTEXT} 0 "STR:$(^NextBtn)"
${Else}
SendMessage $0 ${WM_SETTEXT} 0 "STR:$(^InstallBtn)"
${EndIf}
FunctionEnd
Function directoryPreA
# Skips the directory page for A if not chosen for installation.
${IfNot} ${SectionIsSelected} ${SEC_A}
Abort
${ElseIfNot} ${SectionIsSelected} ${SEC_B}
GetDlgItem $0 $HWNDPARENT 1
SendMessage $0 ${WM_SETTEXT} 0 "STR:$(^InstallBtn)"
${EndIf}
FunctionEnd
Function directoryPreB
# Skips the directory page for B if not chosen for installation.
${Unless} ${SectionIsSelected} ${SEC_B}
Abort
${EndUnless}
FunctionEnd