As stated by Logophobe below, you can of course substitute ingredients as you like. I personally find subbing beef for lamb or vice versa a bit risky though.
Lamb in general has a much milder taste of itself and thus requires a sauce and other accompanyments that do not overpower the taste of the meat. In your case this could mean that the sauce will be too weak as an accompanyment to beef.
In a case such as this and not knowing the actual recipe I would suggest replacing the Pinot Noir with a somewhat more fragrant red wine (a new world Merlot low on tannines should do nicely). You could also make the sauce more rounded by adding some crushed juniper berries.
Should you want to stick to your original recipe, you might try just reducing the sauce a little more than you usually would.