To build a Gantt chart to show a time schedule, you can use Conditional Formatting with a formula based on AND and OR functions. In the example shown, the formula applied to D5 is:
=IF($B5<$C5,AND(D$4>=$B5,D$4...

To evenly distribute a payment or other amount over a given number of months, with a variable start month, you can use a simple formula together with the AND function and a bit of boolean logic. In the example shown,...

To test a cell to see if contains certain words but not others, you can use an array formula based on the COUNT and SEARCH functions, wrapped in the AND function.
In the example shown, the formula in C5 is:
{=AND(...

If you want to use conditional formatting to highlight cells that are NOT between two values (a lower and upper limit), you can use a simple formula that returns TRUE when a value meets that condition. For example, if...

To allow only unique numbers in a given range, you can use data validation with a custom formula based on the AND, ISNUMBER, and COUNTIF functions.
In the example shown, the data validation applied to B5:B9 is:
=AND(...

To highlight intersecting row(s) and column(s) with conditional formatting based on exact matching, you can use a simple formula based on mixed references and the OR function.
In the example shown, the formula used to...

To test if a numeric value falls between two numbers, you can use the AND function with two logical tests. In the example shown, the formula in E5 is:
=AND(D5>MIN(B5,C5),D5<MAX(B5,C5))
How this formula works...

To display a conditional message, without the IF function, you can use boolean logic and the REPT function. In the example shown, the formula in D5 (copied down) is:
=REPT("low",C5<100)
If the value in...

To set a check register formula that calculates a running balance, you can use a formula based on simple addition and subtraction.
In the example shown, the formula in G6 is:
=G5-E6+F6
How this formula works
The...

To build a Gantt chart by week, you can use conditional formatting applied with a formula based on the AND function. In the example shown, the formula applied to D5 is:
=AND((D$5+6)>=$B6,D$5<=$C6)
When the...

To run a formula only when one or more cells are not blank, you can use the IF function with an appropriate logical criteria. In the example shown, the formula in E5 is:
=IF(COUNT(C5:C7)=3,SUM(C5:C7),"")...

To check if a date is within the last n weeks of today's date, you can use a formula based on the AND, TODAY, and WEEKDAY functions. In the example shown, we are testing for dates in the last 2 weeks. The formula in...

To test for various combinations of this AND that, or this OR that, you can use the IF function with the AND and OR functions. In the example shown, the formula in D6 is:
=IF(AND(B6="red",OR(C6="small...

To highlight rows and columns associated with an approximate match, you can use conditional formatting with a formula based on the LOOKUP function together with with a logical function like OR or AND. In the example...

To allow only whole number percentages like 5%, 10% and not 5.5%, 10.25%, etc. you can use data validation with a custom formula based on the TRUNC function. In the example shown, the data validation applied to B5:B9 is...