\setupinteraction[state=start]

\starttext

\setupfield
[ShortLine]
[label,frame,horizontal]
[offset=4pt,height=fit,framecolor=green,background=screen,backgroundscreen=.80]
[height=18pt,width=80pt,align=middle,background=screen,backgroundscreen=.90,frame=off]
[height=18pt,width=80pt,color=red,align=right,style=type,background=screen,backgroundscreen=.90,frame=off,regionin=JS(Initialize_TeX_Key),afterkey=JS(Convert_TeX_Key),validate=JS(Convert_TeX_String)]

\definefield [Email] [line] [ShortLine] [] [pragma at wxs.nl]

\field [Email] [your email]

\stoptext