I wouldn't count on Prunus tomentosa fertilizing the flowers of P. avium. Instead I would make sure one of the P. avium cultivars listed as being suitable for 'Bing' - whatever those might be - was present. If you haven't already, try looking on the web for cherry pollination chart.

Thank you! I was able to get a hold of the nursery where the Bing is coming from and added a Black Tartarian to the order. I looked at a cherry chart and they are compatible. Thank you for the suggestion! I would have been disappointed next year with no cherries! They are both 5 ft dwarf trees. Do you have any advice on cherries? I have the nankings but they are easy.