Increment Bookmark name?

I have an english and a spanish version of a word form. I have created
a macro to check the corresponding box in spanish when the english box
is checked. However, the bookmark name is hardcoded in the macro so
the macro only works on the first box of each version - checkbox1 and
checkbox76. Is there a way for me to have the macro increment the
bookmark name so it correctly marks the checkbox? Such as:

{checkboxname}
{checkboxname} + 75

or some better way?

Thanks!
Jason