On the `WizardForm.InstallingPage`, the `WizardForm.FilenameLabel` automatically truncates the string containing the file path, to include the drive letter at the beginning, followed by the maximum displayable path, truncating from the top level of the path, to fit the size of the label, so that the file name is always shown e.g. `C:\...\LongFilePathNameWithMultipleSubDirectories\Filename.ext`. 

I have looked at the `Length`, `Pos`, `Copy` and `ExtractFileDrive` String Functions, but given that there are an almost infinite number path and file name possibilities, as the user can choose any installation path they wish, I am struggling to work out a way to show the maximum possible length of the path, without truncating the file name. 

I think I need a function like `Pos` that returns the number of matches and the index for every `\` it finds, which would mean I could use `Length` between each index to determine where to `Copy` from, but I haven't been able to find any way of doing this.