Going through your XAML I found two things.
Your condition 'cellValue.Trim=" " ’ there is a space in your condition after the trimming the string so you should indicate a string without spaces to check for an empty string. (Or you can try IsNullOrEmpty / IsNullOrWhiteSpace if you are so inclined towards checking for white space.)
The second one, is instead of doing a separate activity of getting the row item using the column name I have attached a sample which might help your perspective of whatever you are trying to achieve (Which I might add uses the Column name to check for the incoming value) . : Sample.zip (29.9 KB)
Hope this helps.