currency convertor issue

I don't think that would work (in all scenarios) given it would be dependent upon client locale.

For ex. this works for you because € is default system currency thus cells formatted as Euro's return a cell format of C# (where # is determined by decimals used) whereas all other currencies return ,#, however, in the UK given £ is default system currency both Euro and USD would return ,# and only £ would return C#

Also given # you would probably want to revise the approach to check only for existence of C in format given the no. of decimals may vary.

(If the client is set to use $ as system currency then (reversed) it could work of course)