Create an error message

Hi,

I am trying to create a pop up error message using data validation, however as both cells I am using contain formulas it will not work. I have come accross a few posts that have had a similar problem and the suggestions have been to use VBA. I have never used this function in excel or macros before. Can anyone help me here.

Ultimately what I would really like to happen is, I have a reference table on the reference page, which shows a rate code and the age you need to be to be on this rate code.What I want to happen on the Darwin rosters page is that if the rate code (f7) for the employee does not match the age in cell (G7) based on the reference page then create an error.
So the only way I could work out to do this was to create another column that looked up the rate code on the reference page and populated the age, therefore I would then have two columsn to compare and create the error message, but as the Data validation will not work on a formualted cell, I am at a loss.
I have attached the workbook I am using, it is for labour management. So on the Darwin rosters page. What I want to happen is if cell H7 is a lower value than G7, I want an error message to pop up and stop the user from continuing until they change the grade that has been selected.

Can anyone help??

At what point do you want to data validate if H7 is lower than G7? When the user enters data in column E? or F?

What is this grade change that you indicated?

To someone who does not know your sheet or your process it is very confusing.

Ok so the rate code in column F represents a rate of pay in our payroll system. There is a different rate code depending on the age of the employee and the level that they are employed at.
So basically, if at any point the rate code that the employee is on (for example, the employee is 20, but the rate code they are on represents a pay level lower than there age) a error message should come up. The user also has the option of a rate overide, to allow them to pay an employee at a different rate, if the user uses this, the rate code in column F will automatically change to represent the rate. But the same principle, if a rate code selected represents a lower age than the actual employee, an error message should appear warning the user.

It is very confusing, this is why I thought if I have the two columns, G7 which represents the employee age, and then H7 which represents the age of the rate code. So if the the age on the rate code is lower than the age of the employee, then this is where the error would appear. If that makes sense...

Can no one help?