want to add '-' to count the 6th data from the left.

[Sxbbb]

I have a field 'Lot '

in field  'Lot ' contains data :

want to add '-' to count the 6th data from the left.

EX

165052171

A0172050012

[MarcoWedel]

Where is the '-' sign in this example?

[Sxbbb]

EX

165052-171

A0172050-012

[MarcoWedel]

How does  '-' "count the 6th data from the left" in these examples?