use conditional formatting to enter a value in a cell

[jrg24]

I do not know if this is possible but it would be really cool if it was. Is there a way to insert a value of a cell based off of the value of another cell the same way conditional formatting can apply formatting based off of the value of anther cell?

I have created a form that creates additional fields depending on the entries made to other cells. In Cell A1 the user selects a number of 1 thru 10 from a drop down box via data validation. This will create a list of items below cell A1 depending on the number selected (1 item list if 1 is selected, 2 item list of 2 is selected, etc.). The user is to then enter some data in column B next to each listed item in column A. What I want to happen is for the values in column B to always be blank unless there is a corresponding value in column A. So for instance, if a user selects the number 3 from the drop down box, then the value of where he would enter data for item 4 would always be "" regardless if he types anything in the cell. in essence, if cell A4 is blank, then cell B4 should always be blank regardless of user input. Is that possible?

 

[oldbrewer]

paint B4 black if A4 is blank to remind user not to put a value in there or "do not enter a value here"

 

[jrg24]

paint B4 black if A4 is blank to remind user not to put a value in there or "do not enter a value here"

I was going to use a data validation error message if I had to but I have been using conditional formatting a good bit on this sheet and it got me to thinking about the possibility of setting a cell value based on the existence of data in another cell. Also, I cannot use text in column B because caluclations are happening based on user input.

 

[oldbrewer]

any formula in a cell is overwritten if user overtypes it, or give the user somewhere else to enter the data and if it is ok the formula in the cell would pull it over else leave it blank.....