solved my question .. i was looking into wrong parameter (pobjects Par6 was not a DoubleValue). 

Hi Jozef,

When I’m dealing with changing cells in an editor that could take multiple values (i.e. the parameters in the LDE/NCE or the Hx/Hy/Px/Py/Ex/Ey columns in the MFE), I always like to wrap my cell assignment in a short switch statement.  All cells in the API can have 1 of 3 values:

• ZOSAPI.Editors.CellDataType.Integer
• ZOSAPI.Editors.CellDataType.Double
• ZOSAPI.Editors.CellDataType.String

If the current is expecting a different data type than what you are assigning, you will get the error you saw.  A short pseudo-code (sorry, I don’t know Mathematica) would then look like:

switch(cell.DataType){

   case ZOSAPI.Editors.CellDataType.Integer:

      cell.IntegerValue = val; break;

   case ZOSAPI.Editors.CellDataType.Double:

      cell.DoubleValue = val; break;

   case ZOSAPI.Editors.CellDataType.String:

      cell.Value = val; break;

}