Yes/No Pop-up Window

I have a certain macro which copies data from one file to the other. There are several target files (refering to a given month each) and one source file. The user chooses a month from a drop down list in the source file which modifies a certain cell. The value of this cell decides on which of the 12 target files will be opened to paste the data to. The macro also copies the value of a cell which refers to the current date (=TODAY()) This number is then compared with a the range (value between two pints in time: start and end date of a given month). All I need is some sort of a pop-up window with a header i.e. WARNING. and the window text: You are about to send the information to a file which does not refere to the current month, are you sure you want to perform this action" and two buttons YES and NO in case the value of the current date does not match the range set up by the starting and ending of a given month in the target file. The button YES would then do waht ever the code that was placed before the pop-up window said, save the aplication and close it, and the NO button would simply close the aplicatiown without saving it. Something like that:

Sub Export()
'the whole code describing the action to be taken
If Range("A1").Value >= Range("A3").Value And Range("A1").Value <= Range("A2").Value Then
'here the A1 cell refers to the current date and cells A2 and A3 to the start and the end date of the month
End Sub