Locking onto 1H signal in Bruker TopSpin

Hi,

I have to monitor a reaction in THF, but I ran out of THF-d8. I'm having issues running unlocked on our machine due to magnetic drift. We have very limited NMR solvents in our glovebox right now (because I used them all, lol) and I don't have time to dry and freeze-pump-thaw more in. I was thinking about spiking the THF with some benzene-d6 but I'm worried about solubility of my product.

Is there a way to lock onto the THF 1H signal? I know it's possible to shim using the 1H signal, but I haven't seen a way to lock onto it.

Any help would be appreciated.