I have two tabs. The one tab contains a complex model ("Model"), and the
other is a control or summary ("Control") of key values and settings in the
model.

I want to be able to change the key values in either the "Model" tab, or
"Control" tab. If I have the Model tab refer to the Control tab for these
values, it gets really annoying to trace formulas. If I have the Control tab
refer to values in the Model tab, it is annoying to have to go to the Model
tab to change the value. I want to be able to look at the Control tab and be
able to change values, and I want to be able to look at the model tab and
change the same values. By definition I want the cells on the two sheets to
behave as if they are the same cell.

Please help!!!