property Pattern: LongWord;

Pattern can be one of these XlPattern constants.

xlPatternAutomatic xlPatternChecker xlPatternCrissCross xlPatternDown xlPatternGray16 xlPatternGray25 xlPatternGray50 xlPatternGray75 xlPatternGray8 xlPatternGrid

xlPatternHorizontal xlPatternLightDown xlPatternLightHorizontal xlPatternLightUp xlPatternLightVertical xlPatternNone xlPatternSemiGray75 xlPatternSolid xlPatternUp xlPatternVertical

This example adds a crisscross pattern to the interior of cell A1 on worksheet one.

Workbook.Worksheets[1].Range['A1', 'A1'].Interior.Pattern := xlPatternCrissCross;