I want to update custom formulas added my Excel add in. Using Application/worksheet.Caclulate() updates whole sheet, but I want to update only those cells which are using my formulas.
I haven't tried this, but what if you used the technique described in Get formulas from a range of cells on the entire UsedRange of a worksheet. Then iterate through the returned array to find all the cells that have formulas matching one of yours. Then for each of those cells, call Calculate().