It seems the .cab file has to be installed under PE mode, not during a logged in session. Never mind.
I have another question - I have tried to tailor your example to substitute RegionValue for OSDComputName variable (which is declared in PE environment before the OS is deployed) . So, if OSDComputerName like TOK , then Japanese language settings are applied etc. I have read that SCCM can't handle 'like' or 'contains' queries (and for reference, I used a Custom Variable, same as you do) to declare OSDComputerName. I'm now finding that the components aren't installing, but no idea where to check on client logs where this went wrong, and why.
We want to build PC's by the region, and SCCM to detect the OSDComputerName, then apply the relevant language packs and UI languages depending on this variable.
Do you know which logs to check, or anything to watch out for when doing things this way? I think the reason my deployment failed has something to do with OSDComputerName not being a custom variable, but I'm not sure how i should declare this in the:
IF OSDComputerName like TOK THEN
SET OSDLanguage to ja-jp
Declarations...
attached example