Get low/high value of the bar before entry bar

Question

In my strategy on TV I want to get the low/high value of the bar whose condition was used to trigger order entry. Since TradingView places order entry on the following bar, I think i need to get the value of previous bar. I tried this:

firstEntryBar = strategy.opentrades.entry_bar_index(0) + 1
entry_low = low[firstEntryBar]
strategy.exit("Take Profit/ Stop Loss","Short", stop=entry_low, limit=short_take_level)

However the code above is not working and SL gets triggered right at order entry.