How can I disable a cell so that the user cannot click into these cells at all. Also when the user navigates through the grid these cells shall be skipped.

You can disable cells with SetEnabled(FALSE);

It is not possible to position the current cell onto a disabled cell. When the user navigates with arrow keys through the grid disabled cells will be skipped. When the user clicks with the mouse into a disabled cell nothing will happen.

It is recommended that you set disabled cells also read-only. Otherwise the user can select a range of cells and presses DELETE to clear all cells in the selected range.

Example:

SetStyleRange(CGXRange(1,1,CAL_ROWS,CAL_COLS), 
CGXStyle( )
      .SetEnabled(FALSE)
      .SetReadOnly(TRUE)
      .SetFont(CGXFont( ).SetBold(TRUE).SetSize(10))
      .SetInterior(RGB(192,192,192))   // light grey
      .SetHorizontalAlignment(DT_CENTER)
      .SetVerticalAlignment(DT_VCENTER)
   );