Actually, I finally found the 'Rslash' option in the 'Handle String...' function that did what I want after more digging around.

I just needed to accommodate the outliers, like someone selecting a root directory. In that case, SB7 sets the install folder is set to (for example) "E:\", whereas selecting any other subfolder sets the install folder to "E:\MyFolder" (note no backslash.)

Thanks again,
Tom