Hi,

Another way would be to use Data/Validation. In a blank cell say N1 you
would type =AND(A1<0,B4=""), this will result in a TRUE or FALSE statement.
Next select all your input cells and goto Data/Validation, select "Custom"
from the list and type =$N$1=FALSE, next click on the "Error Alert" tab and
type a small message to let people know what they should do or why they
received the alert message. So if A1 has data and B1 is blank then an error
message will pop up when trying to input data into the other input cells.


HTH
Jean-Guy

"Jeff" wrote:

Hi,

I like to know how do I set up in excel to setup a field to be a mandatory
field if the field beside it has data ?

For example: If A1 has data, A2 can not be a blank field and prompt error
message.