Nice oxen!

John Frame lists a fourfold distinction that theologians have recognised with regard to our desires [many of which are right and legitimate: the desire for blessing from the Lord (Deuteronomy 28; Mark 10:29-31), for food (Matthew 4:2), for drink (John 19:28-29), for sleep (Luke 8:23), for sex (Genesis 2:22-23; Song of Songs), for children (Genesis 30:22-23; 1 Samuel 1:17; Psalm 127:3-5), for a better house (Proverbs 24:27), to be an overseer (1 Timothy 3:1 & 1 Peter 5:2).

Here it is, not quoted exactly, but quoted with the adjustments that he then makes later in his chapter:

1. Spontaneous desire (one that catches you off guard)

2. Nursing that desire (sometimes called titillatio)

3. Making a plan to achieve it unlawfully

4. Accomplishing the desire. 

The key word is under 3. Unlawfully. 
The problem isn't that my neighbour has a nice ox and I admire it and want one like it. The problem is that I think about stealing it, or defrauding him of his ox in some way. Frame illustrates this with regard to lust: 

Lust is sexual coveting. It is not wrong, say for Chuck to desire a sexual relationship with Alice, given that both are single. That is a God-given incentive towards marriage. It is wrong for him to desire sex with her apart from marriage, for that is a desire to violate God's law.

(p846-849) DOCTRINE OF THE CHRISTIAN LIFE (Theology of Lordship)