Your Integer will overflow outside the range -32,768 to +32,767
A Long Integer's range is -2,147,483,648 to +2,147,483,647
If the decimal section isn't necessary with the DSum() rounded, then Long should be Ok.......Unless of course you are doing something for Amazon
As the theDBguy said a Currency will solve your problem.
Or a use Single which gives +-3.402823E38 with 6 digit precision. Or a Double +-1.79769313486232E308 with 10 digit precision.
I tend to use Long Integers unless I know an Integer will definitely be Ok. There is a small saving with Integer over Long Integer, but in most cases space is unimportant.