Record Time And Date Of Data Entered Into Workbook?

I'm having trouble while trying to use a variable in a cell reference. I have a sheet that is being used to record the time and date of data entered into the workbook. This sheet is divided into columns, each designated to a specific type of data. I have written a macro to enter the current time in the correct column, but that macro is embarrassingly long and complicated because I used a series of if statements to handle all the different data being entered. I'm trying to simplify by using vlookup, and assigning the column value to a variable, and inserting that variable into the cell reference.

Here is the line I need to insert a variable into:

Sheets("Current").Cells(Rows.Count, columnstart).End(xlUp).Offset(1, 0).Value = Now()

Where columnstart is my variable. It is an integer, but it's value will change depending on the type of data being entered.