User Form Data entry trying to check that Data is entered right

[CityMPLSEmpolyee]

I am trying to make a user form so that the use can enter their data from 1 input box rather then 5
But I keep getting errors

See attached file

[CityMPLSEmpolyee]

For more explanation
In cell C14 I want the user to enter a capital Letter from A-G only
In cell D15 I want the user to enter a number that will be less than the number in cell D16
In cell D16 I want the user to enter a number that will be higher than the number in cell D15
In cell E16 I want the user to enter a negative number or have the form make it negative
In cell F16 I want the user to enter a positive number
When they click apply, I would like the code to check the data, and if any of it is incorrect to instruct the use to fix it

Is this possible?