Partial Caching in User Control based on Session Variable?

[Manish Jain]

I am trying to implement Partical Caching in a User Control that gets data
from DB and populates a combo based on:
1) GroupKey : An int Property that is known for each call (say Source=10,
Code=11 etc)
2) UserID : int, Stored in session

This combo is user specific so that each user has different combo contents
for different groupkeys, but these would not change for the user for a
groupkey.

I have the groupkey part working:

[PartialCaching(300, null, null,"GroupKey")]
public abstract class LookupCombo : System.Web.UI.UserControl

.....

<uc1:LookupCombo GroupKey="7" id="cmbSource"
runat="server"></uc1:LookupCombo>

But I am not able to use the session variable available as a static class
member Settings.UserID (int). What I have is caching working on groupkey so
that all users have the data of the first user.

I tried exposing property for UserID but that doesn't work.

Can someone suggest any solution?

Manish