Formula to catch a change in sign in Excel

[Viva_Excel]

I have a lot of rows data to review and need to make sure that all the data input was input using the correct sign (either positive or negative). For this, if the first month in the row is a positive number, all the remaining data in the same row needs to be positive. Conversely, if the first month in the row is a negative number, all the remaining data in the same row needs to be negative. There are times when people make mistakes and make mistakes. Thus, I am trying to come up with a way to check if there has been a mistake. Is there a formula I can use to make sure that the data is either positive or negative (maybe using conditional formatting so I can quickly identify which cell changed?). For example, if month one is $100 but month ten is input as -$100, I want to be able to identify cells where the sign used has changed using some sort of formula. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>