Compare Columns A& B on Sheets M and D, if A matches and B doesnt Copy B, else new row

[Spyderz]

Thanks for stopping by first of all. so I'll try to be Clear. I'm certain its simple for someone, but definitely kicking my butt this week.

I would like to compare 2 columns A and B in sheets Master(M) and Data(D), if the data matches in A, Check B, if B matches, go to Next. If Not, update Master(M) B with the values from Data(D) B, but if the values from Data(D) don't match in A or B, Add a new row to Master(M) from the unmatched row.

so Master(M) holds all the info, if Data(D) has a new listing in column A, add a Row in Master(M) with A and B from data, otherwise just Update B in Master(M) from Data(D)