Execute Cell with a Macro (timer)

Hi
I am learning guitar and I felt that if I use random chord names by using a timer say 10 seconds to auto change the chord in Excel, I could increase my speed of changing chords. I have list of chords in A1:A17 and this formula =INDEX(A1:A17,RANDBETWEEN(1,COUNTA(A1:A17))) entered in C1.
What I want is a Macro with a timer to run the above formula every 10 seconds and auto change the chord in cell C1. The macro to include Start and Stop button, if possible.
Let me know where to insert the macro in the workbook.
Any help would be appreciated.
Thanks
FLDS

Note: I have posted this same request in Mr Excel forum, NO replies