Update textbox during runtime

Hi,

I have a windows form application which can sometimes perform a number of complex calculations, which can take several seconds to complete.

I would like the user to be aware that the program is calculating, and not actually crashed, so I wish to have at several intervals a textbox notification which updates with information during runtime, e.g. "Optimising", "Analysing","Complete".

However, I've noticed that the textbox will only update with the text once the program is complete.

The program runs in a linear fashion, i.e. one Sub for Optimise, which then passes to one sub for Analyse, which then passes to one sub for display etc.

Is there any way I can get the textbox to update during the program run? 

Thanks,