lblValue.Text = theWorksheet.Rows[1].Cells[4].Value;
In order to get the evaluated value of an Excel Cell that is represented by a Formula, you simply access the Value property of the WorksheetCell .
The example code below shows you how to access a particular Excel Worksheet Cell that is populated by an Excel Formula.
In Visual Basic:
lblValue.Text = theWorksheet.Rows[1].Cells[4].Value;
In C#:
lblValue.Text = theWorksheet.Rows[1].Cells[4].Value;