Last column always shows null in Datagridview in vb.net -

in datagridview, i'm entering values in each column. on button click i'm calculating these values using formula populating in datagridview.

here have 4 columns in first datagridview, when press button, can first 3 columns value only. when see in watch window, last column value shows nothing.

if delete fourth column , having 3 columns now, third column value shows nothing.

how can avoid this?

my coding

for irow = 0 logcalcenter.rows.count - 1             if (trim(logcalcenter.rows(irow).cells(0).value) <> "" , trim(logcalcenter.rows(irow).cells(1).value) <> "" , trim(logcalcenter.rows(irow).cells(2).value) <> "")                 dim sw decimal                 sw = logcalcenter.rows(irow).cells(2).value                  rowindex = logcalvalue.rows.add()                 dim newrow new datagridviewrow                 newrow = logcalvalue.rows(rowindex)                 newrow.cells(0).value = fa.text * frw.text / ((sw ^ fm.text)) ^ (1 / fn.text)                 newrow.cells(1).value = logcalcenter.rows(irow).cells(1).value                 newrow.cells(2).value = logcalcenter.rows(irow).cells(2).value * logcalcenter.rows(irow).cells(1).value                 newrow.cells(3).value = newrow.cells(0).value * newrow.cells(1).value             end if         next irow 

here logcalcenter.rows(irow).cells(2).value return nothing.