How to move stoplimit thresholds?

Dear all,

after having placed a stoplimit order in quantstrat, how can its 
threshold be changed later on?

Example: I have placed a market order together with a stoplimit order at 
some threshold. As soon as the trade has moved into the positive by a 
certain amount, I would like to move the stoplimit closer to the entry 
price.

I would be very grateful if somebody could provide an example. Thank you.

Heiko