This code will update every record with the same value,

Code:
"UPDATE adjAssembly " &
                                   "SET colAmount=@amount,colUnit=@unit"
You need to identify the record you want updated, usually there is a PrimaryKey

Code:
"UPDATE adjAssembly " &
                                   "SET colAmount=@amount,colUnit=@unit WHERE yourIdField= @IdParam"
But if you are using a DataAdapter to retrieve the data then it would be easier to us the DataAdapter Update method.