Sorry if the code above was inaccurate, here it is:

ActiveCell.FormulaR1C1 = "=DATE((MID(R[-1]C,5,4)),(MONTH((DATEVALUE(MID(R[-1]C,FIND(""th"",R[-1]C,1)+3,LEN(R[-1]C)-(FIND(""th"",R[-1]C,1)+3-1))&1)))),(MID(R[-1]C,10,(FIND(""th"",R[-1]C,1)-1-10)+1)))"

Here's what the formula should come out as:
=DATE((MID(D1,5,4)),(MONTH((DATEVALUE(MID(D1,FIND("th",D1,1)+3,LEN(D1)-(FIND("th",D1,1)+3-1))&1)))),(MID(D1,10,(FIND("th",D1,1)-1-10)+1)))