Use the fixed melee damage field (wFixDamage) and remove the wMain.? tag. You can put whatever you like into wFixDamage and it will get displayed.
Code:
~If we're not shown, just get out now
doneif (tagis[Helper.ShowSpec] <> 1)
~ if we've been disabled, get out now
doneif (tagis[Helper.SpcDisable] <> 0)
field[abDuration].value += round(field[xTotalLev].value/8,0,-1) + 1
field[abValue].value += hero.childfound[aINT].field[aBonus].value
field[abValue2].value += hero.childfound[aSTR].field[aBonus].value
field[abValue3].value += field[abValue].value - field[abValue2].value
field[wFixDamage].text = field[abValue3].value