Largrangain Multiplier as State Variables?

Hi all,
Usually Largrangain multipliers appears as static or forward-looking variable. But in my model, Mu(-1) appears...
Could a Largrangain multiplier be a state variable ? How to understant it ? Is Mu(-1) determined in the end of last period ? Standing at period 0, is Mu(-1) determined in period -1 ?
But Mu(-1) is determined before I make any decision. If no decision was made, there is no optimization, and hence no Largrangain multiplier existing....
So...Mu(-1) makes no sense, isn't it ?
Thanks!
Usually Largrangain multipliers appears as static or forward-looking variable. But in my model, Mu(-1) appears...
Could a Largrangain multiplier be a state variable ? How to understant it ? Is Mu(-1) determined in the end of last period ? Standing at period 0, is Mu(-1) determined in period -1 ?
But Mu(-1) is determined before I make any decision. If no decision was made, there is no optimization, and hence no Largrangain multiplier existing....
So...Mu(-1) makes no sense, isn't it ?
Thanks!