I need some help.

My boss has asked me to find out how to do something in Excel and I have yet to figure out the solution. Here is the situation: we do Estate Plans for people, mostly married couples. On one sheet of a workbook we have the couple's assets and how they are owned. For example, "Assets owned by Ken's Trust"; "Assets owned by Barbie's Trust"; "Assets held by Ken"; "Assets held by Barbie"; "Assets held jointly" etc.

On the next sheet we have a flowchart that will show how the assets transfer. For example, "At Ken's Death" could flow to two boxes "Assets to Ken's Estate Trust" and "Assets to Barbie".

What I need to do is figure out two things:
(a) how to link the numbers from the spreadsheet to the flowchart so that if I change the numbers on the spreadsheet they update on the chart, for example if I change "Assets owned by Ken" from $250k to $500k; and
(b) how to enter a formula into the flowchart that will calculate numbers based on numbers from the other box in the flowchart, for example "if Assets to Ken's Estate = greater than $500k, calculate 45% tax; if less than $500k calculate 35% tax."

I really need some expert help on this. I have some experience with Excel but, obviously, not a ton. If someone can help me, I would GREATLY appreciate it. The more complete and step-by-step an answer can be, the more I will be able to follow it.

Thank you for reading my thread.

Paula