Here's a snippet of code to get you started. I created a spreadsheet called delme.xlsx. In cell A1 I put the value 1. In cell A2 I used the formula "=PI()". I named cell A1 "Value1" and cell A2 "Value2". In cell A3 I used the formula "=sum(Value1,Value2)".
fname = 'c:\temp\delme.xlsx';
xlObj = actxserver('Excel.Application');
xlObj.Visible = 1;
wsObj = xlObj.Workbooks.Open(fname);
Sheet = wsObj.Sheets.Item(1);
A3_value = Sheet.Range('A3').Value
A3_formula = Sheet.Range('A3').Formula
A3_value is equal to 4.141592653589793 and A3_formula is the string "=SUM(Value1,Value2)".
Hopefully this helps,