advertisement reference

Hi,

I had to spend a few minutes trying to work out what is the next reference I could use in the ad.
I searched for the current requisitions and saw that there were 4 returned including the current one.
So I entered MC1849D - not unique.
I had to submit the ad all the way to H (5 times) to get the next available one.
Can we not have a simpler way of checking or letting us at leas know what is the next available ad reference number?