[P-Marlowe]

Michael Horton, in his White Horse Inn series Reforming Worship, put it this way: God is a machine, predictable. If we do x, God will do y. God is reacting to what we do.

If God promises to do x if a man will do y and when a man then does x and God does not do y, then what is God?

[Lexinom]

In the paradigm set forth you've essentially set man up as the prime-mover, aka God.

If man does x it is because God, the prime mover, did w. To say otherwise is rob God of His power and glory.

[nobdysfool]

If God promises to do x if a man will do y and when a man then does x and God does not do y, then what is God?

In this case, a lot more perceptive than you. If it is God who promises to do x, then for man to do x means that x is not anything supernatural, otherwise only God could do it. If God promises to do x if man does y, then if man does x, there is no need for God to do y. Man has done it all!