Hi,
1. In Excel choose Insert, Symbol, from the Font drop down pick Symbol,
scroll down to find it, its symbol 185.
2. You can type =CHAR(185) in a cell and then format the cell with the
Symbol font set.
3. There will be and Alt+ Number Key Pad combination, but I can't test it
easily on my laptop.
4. In Excel 2007 choose Insert, Symbol and with Font of Arial and Unicode
(hex) selected it far down, character code 2260.
Of course none of these will be useful in formulas.