Concure...maybe you could post the actual spreadsheet. Your post #7 should have worked.
Expr4: Mid([Installation Date1],3,2) & "/" & Left([Installation Date1],2) & "/" & Right([Installation Date1],2)
In order for you to get 1119/11/19 you must have not used the above formula....
instead...
Expr4: Mid([Installation Date1],3) & "/" & Left([Installation Date1],2) & "/" & Right([Installation Date1],2)
Omitting the ",2" is the only logical problem and easy to make that mistake without any error.... (IIRC)