setting an environment variable on target computer

hi folks - my first post here.

i've successfully deployed my app to a clean computer. because of the libraries i'm using (root.cern.ch) i have no choice but to insure that a new environment variable is set on the target computer during the installation (i'm using MSI not clickonce). i also have to append to %PATH% on the target computer....

after quite some searching, i understand that i must edit the environment table in the msi file. i opened the installer in orca.exe, and i can see the Environment table, and i know i need to add 2 rows there. but after a lot of reading i am still very unsure what 4 strings need to be in these rows!

i.e. i want the name of the environment variable to be ROOTSYS, and its value to be [TARGETDIR], but i don't know what to put in the "Environment" and "Component" columns..... i RTFM and everything google can find but it's still not clear to me what the "primary key" and "external key to component table" columns are, respectively.

for appending to the path, i assume i just define a 2nd row in the Environment table, with name PATH and value ;[TARGETDIR]\bin\ but still i am not clear on the other columns...

i see the WriteEnvironmentStrings action (condition= empty, Sequence= 5200) and the RemoveEnvironmentStrings action (condition= empty, Sequence= 3300) in the InstallExecuteSequence Table, so i guess that part is all set.

any hints would be greatly appreciated! - newbie

p.s. BTW: Visual Studio Standard, both dev and target machines are XP Pro, validated & w/ all updates.....

i'll answer my own question.... i opened my msi file in InstallShield Pro, added&appended to some env vars, saved the msi file, then i opened it back up in orca to see what it did.... ham-handed, i know, but this helped give me some hints.... after some playing around a little & testing, the 4 columns i need are

where C_yadayadayada i got this way. click on Component table on left-hand side in orca, & on right-hand side, look for the row that has TARGETDIR in the Directory column, then copy the value from the first column of this row to the clipboard and use that in the 4th column in the new rows of the Environment table....

i'm too scared to try "=-*PATH" for the second row above. i read somewhere here that i might end up deleting the path string completely upon removal of the deployed app from the target computer (making it unbootable ).... something to test another day... cheers