Start Grid

Begin Again: Reloads the initial values.
Run Start Grid: The initial condition has single digits in cells which can be eliminated from its row & column.
Reset Colors: Removes any highlighting. Useful for actions that do not depend on highlighting: 3 & 4 cell chains.
Row Pairs: Displays a 2nd grid with just the rows with either 1,2 or 3 occurrences of the selected digit. More on this later.
Column Pairs: Displays a 2nd grid with just the columns with either 1,2 or 3 occurrences of the selected digit. More on this later.
Save & Reload Grid: Allows user to save & reload at critical moments during the solution process.
Numeric Buttons 1-9: Highlights the cells with the selected digit. Click 1 to highlight all cells with a 1.

When I solved extremely difficult grids on line, I used "manual" highlighting to clarify the strategy targets.
The application described here automates the highlighting using MS Access & VBA code.
- If a target digit occurs in 2 cells in a row or column then there is a possible 2 cell chain.
- With 2 target digits in a row or column, then there is a possibility of x-wing. More on this later.
- With 2 or 3 target digits in a row or column, then there is a possibility of swordfish. More on this later.

MXQ