Knightmare, unfortunately it's not possible to change the values of any elements or controls in the skin options without actually changing the Options.xml file (or whatever your options file is named), it's just a limitation of the current skinning system.
Your best choice based on the screenshot you provided is to just combine it all into one so that you just 'choose a hero/heroine' (and have both males and females together in the combo box) instead of having to select hero/heroine first then choose from the list.
I assume the only reason you're not doing this as of yet is because you want to be able to determine whether the user has selected a hero/heroine so that you could for example change a background colour between blue (male) and purple (female) or something along those lines. The only solution for that is to just include all of the heroes' names in your conditional tags:
code:
<*PlusSkin Conditions(Hero = "Batman" OR Hero = "Silver Surfer")*>
<element background=rgb(0,0,255)>
</*PlusSkin*>
<*PlusSkin Conditions(Hero = "Spidergirl" OR Hero = "Wonder Woman")*>
<element background=rgb(160,32,240)>
</*PlusSkin*>
/ 
