For sure your DAC don't work with pure serial communication. It can be an I2C or SPI (some company use other notation as 2-wire, 3- wire, serial, Microwire...)

By reading your code, your DAC is certainely an SPI one. In this case you'll have to use SHIFTIN and SHIFTOUT.

With the above you'll be able to shift your 10 bits

Will look something like SHIFTOUT DI,CLK,mode,[Myvar\10]