Returns the number of sheets in a given reference.
- reference may be given either explicitly (Sheet1.A1:Sheet3.G12) or by name (myref).
- If the named reference contains multiple ranges, the sum of the sheets in each range is returned, irrespective of any duplication.
- returns 3, if Sheet3 follows Sheet2 which follows Sheet1; there are thus three sheets in this range.
- returns 1; G4:H6 is interpreted as a range on a single sheet (the current sheet).
- returns 1; D8 is interpreted as a one cell range, on a single sheet (the current sheet).