Istallation and Update script Problem

Hi,I am new comer of NSIS technology.I have written script for installation and update for a software in different script.Now I want to attach both script in one.If user want to install the software,the installation portion will work and if user want to update the software then update script will work.I define MUI_FINISHPAGE_RUN_TEXT "Create Demo Database" for installation and define MUI_FINISHPAGE_RUN_TEXT "Successfully update your software".I want to write this script into conditional statement.It will change automatically by choice of istallation type.Please help me.