data validation for excel cells integer number and A

It must be a custom validation and here is the logic: =IF(ISNUMBER(B2),AND(B2>=0,B2<=100,B2=INT(B2)),B2="A")

You could also create a List of the 100 numbers and A and use the List option in the DV.

I want to check if the cell is empty or not. In case of NULL, it should throw error.

As far as I can see dflak's formula as-is does as well as is possible in making sure that the current cell is not left "empty". What the "countif" formula that you found does in addition is make sure that the user does not skip any rows. For example if you have valid data in E2:E4 and then try to make an entry in E6 (skipping E5) then you will get a validation error.

If you are designing this worksheet for others to use then I would recommend you create a custom input message which defines what the valid inputs are. I would also create a custom error alert message if you are going with the "countif" addition because if someone attempts to skip a row then the actual error is with the previous cell and not the current cell which is contrary to what the standard error message implies.

Finally in the Data Validation dialog box verify that "Ignore blank" is not checked.

I tried from this link [ . . . ] but it's [countif formula] not working.

Here is dflak's formula with the "countif" addition if you decide you need it.

Formula:

Please Login or Register  to view this content.