Conditionals

Total newb here. I'm trying to get a handle on conditional statements in NSIS.

I want to check if a previous installation of a program exists and go from there:

Section "Parse_Registry"

	; parse registry information to determine if program is already installed

    ReadRegStr $0 HKLM "System\ControlSet001\Control\Session Manager\Environment" "EIDMS" 

	$(If) $0 == ""

	MessageBox MB_YESNOCANCEL "C:\SomeProg has not been created. Would you like to create it now?"

	$(Else)

	MessageBox MB_YESNOCANCEL "A previous version of SomeProg has been detected. Would you like to keep the settings?"

	$(EndIf)

SectionEnd

I included LogicLib.nsh, yet when I compile I receive the error: "Invalid command: $(If)"

Syntax problems or logic problems? Thanks for your help. 😁

Never mind... my monitor is crappy. I was using parentheses instead of curly braces.