If it's coming into Dwolla via your bank, you can see it in the Pending tab after you login to Dwolla. If it's coming from MtGox, well... Just look at your account history and do some accounting.
I think the question was regarding the aggregate amount. If cash in the Twilight Zone of Dwolla -> MtGox represents money intended to be spent on bitcoins, then knowing how much cash was held up trying to make it into buy orders would give someone an insight into future pricing. After all, the number of bitcoins are growing at a known, relatively steady, rate. They are a finite resource. Knowing how much fiat demand was about to be available to fight for that finite resource would be very valuable information.
And, given the increasing coverage in the MSM, one has to suspect that there is a pent up demand working its way into the exchanges.