Sure is, in the load event of your editform just put
thisevent.object.pages("Page1").controls("unknownradiobuttonName").value = true
replace the values in "" with e names of your page and control
If the radiobuttons are not on page1 the you will need to activate that page first then activate page1 after setting the value
eg
thisevent.object.pages("radiobuttonPage").activate
thisevent.object.pages("radiobuttonPage").controls("unknownradiobuttonName").value = true
thisevent.object.pages("Page1").activate
Mick