Get the index of the column in the same worksheet that is farthest away from this column and that is dependent on this column.
int GetLastDependentColumnOffset( DWORD dwCntrl )
Returns last dependent column offset if success, -1 if error.
Worksheet wks = Project.ActiveLayer();
Column colObj(wks, 0);
int nOffset = colObj.GetLastDependentColumnOffset(DOO_ERRORBAR);
printf("Column %u\n", nOffset + 1);
Regarding modifiers: The index returned should be such that, if a column were to be inserted at that location in the worksheet, the distance between any column from the same worksheet that is plotted in some graph and any of its modifier columns used in conjunction with the same dataplot in that graph should not change. This could be rephrased like this: if a column plotted in some graph and all its modifiers associated with the same dataplot are considered as one range, then the index returned
1) should not break any such range in the worksheet
2) it should be to the right of the range containing the column through which the method call is made.