Put into bat, Barbados posted a challenging 174 for six, riding on twin half-centuries by Dilshan Munaweera (50) and Raymon Reifer (60) in their stipulated 20 overs.
Punjab then managed to held on to their nerves despite losing wickets to eventually earn a hard-fought victory, their second win in as many matches in the tournament.
Needing 25 off the last two overs with four wickets in hand, Miller and No. 8 Akshar Patel (23) scored 47 runs off 19 balls to take their team home.
Sehwag and newman Wriddhiman Saha then added another 35 runs before the wicket-keeper batsman was sent back into the pavillion by James Franklin in the eight over.
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Glenn Maxwell (16) then joined Sehwag and the Australian soon started his innings with a boundary. However his stay was short lived as after hitting three fours in eight balls he was caught by Ashley Nurse off Rampaul in the 10th over.
A lot was expected from skipper George Bailey but the Australian could not stay longer as he gave an easy catch to Franklin off a Mendis delivery. Three balls later, Nurse got rid off Perera for a first-ball duck as Punjab were reduced to 131 for six in 16.3 overs.
Stranded on the other side, David Miller then blasted a six and a four spread over two overs but Punjab still needed 25 off the last two overs.
Miller then put the icing on the cake with a six over wide long off as Punjab registered their second win in two matches.