Merging specific cells in rows on certain columns

Merging Cells in Excel.  I have a sheet that has 10 columns.  5 columns (A,B,C,D,and E)  have cells in them that have to be merged.  Column B contains a Project number that will be the deciding factor of which cells need merged.  So if B contains Project number 123 and there are 4 rows for that project then calls in A,B,C,D, and E need merged. I have up to 2000 rows on each sheet.  How can I do this withought merging manually?