HOW DO I WRITE A STRING TO FLAG WHEN A CELL HAS OR 17 CHARACTERS?

Question

HOW DO I WRITE A STRING TO FLAG WHEN A CELL HAS < OR > 17 CHARACTERS?

Answer 1

Hi Tassytiger,
A "string" is just a string of characters. Examples are qwerty, 123abc, 43πbono. there are several ways to write one. A more precise description of your end goal might help answer "How do I write a string."
To the current version of your specific question:
What I actually need to achieve is a situation where, when I enter <17 Char. or >17 Char.
inadvertently then tab to the next cell, I get the following response in the active cell:
The cell immediately below "17 character ID" displays an error triangle. These are shown when the formula in a cell produces an error message. they are system generated and require two things to happen: The cell must contain a formula AND something must have happened to cause that formula to produce an error.
I don't wish to add any columns to my s/s but would like to apply the rule to the current column just as i would change the text or fill colour.
The difficulty there is that a cell may contain entered data, OR it may contain a formula. You want to enter data (a string of characters) and you want to produce an error triangle if that string has more or fewer than 17 characters. Evaluating the length of the string requires a formula. Getting the string into the cell requires direct entry (in your scenario). The two are not compatible within the content of a single cell.
Terry's example uses a formula in column B to measure the length of the string in column A. If the length is 17 characters, the IF statement produces the empty string ( "" ), and the cell in column B appears empty. If the string is not 17 characters long, the IF statement produces the string "Not 17 Chars!"
His formula is easily changed to produce an error triangle in place of "Not 17 Chars!":
B1: =IF(LEN(A1)=17, "",17/0)
In this version, if the length of the string in A1 is not 17 (characters), the formula will attempt to divide 17 by 0, and will produce a 'division by zero' error.
But, as with all of the other suggestions, this one will require a new column to provide space for the formula and it's result.
Changing the text or fill colour can be done using conditional formatting. Changing content of the cell (eg. choosing between the entered string of characters and the error triangle) cannot.
Conditional formatting rules compare the content of a the cell to be formatted with either a fixed value (written into the rule) or to the content of another cell. In my examples (and in Ian's examples) above the rules compared the content of the cell to be formattes to the number '17'. The number was generated by a formula which measured the length (in characters) of the text in the cell where the ID was entered, and reported that length as a number.
A way to show a red triangle using conditional formatting is to use Image fill as the default fill of the cell, then use a colour fill as the conditional fill to hide the trialngle when the conditions are met. Here's the same example as used above, with this technique applied to column B:
The same formula is used in column B as in my previous example. Type size is set to 1 point (note the black dot, visible in the green filled cell) to keep the numbers from obscuring the triangles. The triangles are shapes, inserted onto the canvas (not into the table) from the Shapes button in the tools. Their fill colour has been changed to red, a 12 point exclamation sign character ha been typed into the shape and its text colour set to white, and the triangle's size has been reduced as much as possible without triggering the overflow symbol (boxed plus sigh) to appear.
The triangle image (and some of its white background) was made into a png image file by taking a screen shot, and the image was inserted into all of the cells in the body rows of column B as an image fill, using the Graphic inspector. The conditional format rule below was then applied to the body row cells in column B.
Finally, you can apply conditional formatting to the cell containing the ID. This will still require another column to contain the values to which the content of the ID cell will be compared, but that column may be hidden, or may be located on a separate table.
The method requires an second cell for each cell contining an ID, and uses a formula that makes the contents of the second cell the same as that of the ID cell IF the ID cell contents are 17 characters long.
Here's a sample. Table 1 is column A of the same table as above. Table 2 is a single column table holding the comparison cells.
As in the example above, the cells on table 1 were given an image fill. The conditional format rule replaces that with a white colour fill when the cell contains the same text as its partner cell in Table 2.
This is the rule for cell A2. In A3, the cell reference is to Table 2::A3, and in A4, to Table 2::A4. The cell references in conditional format rules must be edited individually.
Regards,
Barry