You can use the number of elapsed bars:

IF Not OnMarket THEN
    MyProfit = 0
    NewSL    = 0
ENDIF
IF LongOnMartket THEN
   MyProfit = close - TradePrice
ELSIF ShortOnMartket THEN
   MyProfit = TradePrice - close
ENDIF
IF Barindex >= (TradeIndex + 10) AND MyProft > 0 AND NewSL = 0 THEN //Count 10 bars before setting Break Even
   NewSL = TradePrice
ENDIF
IF NewSL THEN
   IF LongOnMarket THEN
      SELL AT NewSL STOP
   ELSIF ShortOnMarket THEN
      EXITSHORT AT NewSL STOP
   ENDIF
ENDIF

or use the MTF support to exactly count hours:

TIMEFRAME(????,UpDateOnClose)
 .
 .
TIMEFRAME(1 hour,UpdateOnClose)
IF Not OnMarket THEN
   MyProfit = 0
   NewSL    = 0
   Count    = 0
ELSE
   Count = Count + 1
ENDIF
IF LongOnMartket THEN
   MyProfit = close - TradePrice
ELSIF ShortOnMartket THEN
   MyProfit = TradePrice - close
ENDIF
IF Count >= 20 AND MyProfit > 0 AND NewSL = 0 THEN //Count 20 hours before setting Break Even
   NewSL = TradePrice
ENDIF
IF NewSL THEN
   IF LongOnMarket THEN
      SELL AT NewSL STOP
   ELSIF ShortOnMarket THEN
      EXITSHORT AT NewSL STOP
   ENDIF
ENDIF
 .
 .
TIMEFRAME(default)
 .
 .