copy common cells and variable range from multiple worksheets to single master workbook

"However, this cell is populated by a formula, so i only need to find the last row with data in that cell."

What does that mean - is column B filled with formulas before values are entered into the other columns? Which column will always be filled in that would show the actual extent of the data entry?

I don't want to find the last row in column B, because it is filled with formulas and then the logic depends on the formula, and checking every cell. What column will be filled with entries that will show the last filled row? For example, if you enter values into column D for every entry, then I would use D to find the last entry.