Buildng millis() function with watch dog interrupt

Hello all together,

It is the first time, that I ask a question here, and I think not the last time. I want to ask, if it is possible to build a function that is showing the milliseconds from the startup of the Microcontroller without one of the both timers, but the watch dog. When my Chip is running on 1MHz, I could set my watch dog to 1ms, and cause an interrupt. Then I would have an interrupt every 1000 cycles. When the interrupt occurs, I just add 1 to a word, and then I always know the Millisecond until the overflow.
Then I have for slow operations like blinking lights a milliseconds function and for faster operation I can use the two timers for pwm.
So I don't want or need working code from you, I just want to know if I go in the wrong direction, and then find it out myself, that is mostly the best way for me in learning things.
Because with a function that is showing the milliseconds (like ms() in Arduino or Energia) and two working timers it would be great for my needs.

Greetings,

Sven