to make all older and non installed catched, use:
Case $NavExecutable < "10.1.0.394" or 10 > $NavExecutable

in the above, 10 is before the comparison (in the second part) and it thus translates the $NavExecutable in that comparison into numeric.
if it is none, it equals zero.
or if it is 10.0.121 it is translated to 10 as "." stops the translation (not a numeric char)
similarly, version 9.0.2 will translate to just 9 and 10 is more than nine.
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