How to declare/use multiple AD MAs inside MVExtenstion.cs

All,

I have a situation where importing users from 4 different forests with the help of 4 AD MAs. What should be the next step to provision these users?

sample code:
-> const string MA_NAME_AD = "AD MA";
-> inside ProvisionPersonAD ()
{
connectedMA ad_ma = mventry.connectedMAs[MA_NAME_AD];
}
kindly guide me and let me know if you need further details?