With all due respect to Alasidman, I do not beleive that it is appropriate in this case to add a column as you have described ...
The criteria of the field indicated should be placed exactly where has been indicated.
the
DateAdd() function can be will be useful but {
Click Here for a list of all functions ... they are in the Help files too} It seems you wish to find all policies that will need to be renewed in the next month, so you will need an upper and lower date boundary, the upper being today and the lower being one month from today. You can use the
Between..And sql construct for that.
As Brian indicated, you should read up to learn how to use the function, plus the excercise in discovering the information on DateAdd() may help you learn how to discover more functions and such ...

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So ... as an example of finding a date value that is between today and one month in the future, you can use something like this ...
Between Date() And DateAdd("m", 1, Date())
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Oh ...
Click Here for one of my primary locations for help ...