AnimationSpeedFactorRange is what you're looking for.
CODE
Draw = W3DModelDraw ModuleTag_Whatever
ConditionState = [conditionstate]
Model = [modelname]
Animation = [modelname].[modelname]
AnimationSpeedFactorRange = [MinFloat] [MaxFloat]
End
End
Replace the MinFloat and MaxFloat with desired speed values (decimal):
AnimationSpeedFactorRange = 2.0 2.0 will be twice as fast
AnimationSpeedFactorRange = 0.5 0.5 will slow it down to half speed