I would then use the UDF DirPlus or something similar to get an array of directories. then...
untested
Code:

$UNC = "\\server\share"
$dirArray = dirplus($UNC,"/ad")

for each $dir in $DirArray
  $Group = 'TNT\' + $dir
  If InGroup($Group)
     Use R: $Server1 + $dir
  EndIf
next


Actually I would use one of the MapDrive UDF for the actual mapping.
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