Macro to keep runing total problem

I have a macro, written by somebody else, that is designed to take a numeric value from an assigned cell, add it to the existing value in another cell and place the new total in that second cell. I needed this as a solution to the hours of overtime in a week being erased each time a new week started, but had to have a way to track the year's total. Here is an example of the code:

For j = 8 To Cells(Rows.Count, "v").End(xlUp).Row
Cells(j, "v") = Cells(j, "v") + Cells(j, "J")
On Error Resume Next
Next j

Cell J8 is the first cell with any data in it to be added, column V (specifically cell V8) is where the yearly running total is kept. The above code works perfectly if the first cell is a number or empty; however, it gives an error - mismatch - if there is any text (other than a number) in the first cell, and only the first cell. Subsequent cells in the column with text do not give an error. Any help on how to modify this code to accept input other than a number in the first cell without giving the error?

Thanks for any help,

CVinje