NSIS:LogicLib: RegIfKeyExists

!include LogicLib.nsh

!ifmacrondef _RegIfKeyExists
!macro _RegIfKeyExists _a _b _t _f
!insertmacro _LOGICLIB_TEMP
ClearErrors
EnumRegKey $_LOGICLIB_TEMP ${_a} "${_b}" 0
IfErrors ${_f} ${_t}
!macroend
!define RegIfKeyExists 'RegIfKeyExists'
!endif

Section
${If} HKCU ${RegIfKeyExists} "software\clients\test"
MessageBox mb_ok exists
${Else}
MessageBox mb_ok doesNOTexist
${EndIf}
SectionEnd