> ... i would like ... a routine that ... would take ... 
> the "total time" (in ms) i want the flashing routine to 
> run for, and divide
> it by "x", to get "t".

You have described the solution within your question.

Question: Given total time and number of flashes in this 
time, produce an expression for the time between flashes

Answer:     t_step = T_total / steps.

Here t = total_time/x

This is basic division.
You can use formal division code to do it or use something 
as simple as repeated subtraction.
Note that the answer will be an integer value so that it may 
take up to just under one step time too little or too much 
depending on your "boundary conditions". Dealing with 
boundary conditions correctly is about half of the design 
task in many cases.
________

' x = number of flashes required.
' total_time is the user provided total flashing period

' t_step is calculate time per step

TT = total_time ' avoid destroying original value

t_step = 0

While  TT > 0
    increment t_step
    TT = TT - x
End
_____________

Tstep will be rounded up so that total time >= required 
time.
You may or may not want to reduce it by 1.
If you want x flashes and are toggling a pin after each 
t_step you will have to halve the t_step value above.


        Russell

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