formula highlight and drag changes

If a box is chosen with a formula in it =sheet2.C50 and I want to drag this formula to repeat in a different box the formula changes to =sheet2.C51 =sheet2.C52 and so on. I want to change this to =sheet2.D50 =sheet2.E50 =sheet2.F50 etc so the letter changes not the number. Is it possible to do this? it would save a lot of time if it is.
Thank you