在installshield基本msi项目中读取对话框响应

i've a dialog box SAPEnv dat has eight radio buttons enclosed under same property named SAPEnviro. what i want to do is to get that value in my installscript and set registry values according to button clicked. i used msigetproperty function but its svproperty argument everytime returns blank. while nvbuff size arguement does return a value depending on size of value being returned.i've a dialog box SAPEnv dat has eight radio bu