Checks if the cell in a cube is writable
CellIsUpdateable(CubeName, Dim1Element, Dim2Element [,?DimNElement]);
Cube - The name of the cube in which this cell exists.
Dim1Element, Dim2Element [,?DimNElement] - Dimension elements which define that cell.
Important - Remember that these dimension elements should be in the same order as in the cube. So if a cube has Products, Months and Calculation dimensions in order; function should first use element from Products, then from Months and then from Calculation dimension
1 - If the cell is writable
0 - If cell is not writable
If(CellIsUpdateable('Sales', 'ProductName1', 'Jan', 'Quantity') = 1);
CellPutN(15, 'Sales', 'ProductName1', 'Jan', 'Quantity');