Calculations Incorrect & Error

[Cheyenne]

I did the caculations of the grid and I'm getting weird resutls.
I press the calc button and numbers appear but the calculations are incorrect
and the numbers appear in the column heading.

I get an run-time error 381 Subscript out of range.

I've been using code like the below to calc the columns

The calculations are returning numbers like I
1.11794274231176e+116 and the column heading changed to 25 from a column label.

Why is it that If I keep pressing the calc button the calc changes?

With MSFlexGrid1
     .Redraw = False
     For x = 0 To .Rows - 1
         .TextMatrix(x, 5) = (Val(.TextMatrix(x, 9)) * 6.5) + 0.1 * (Val(.TextMatrix(x, 10)))
          Next
       .Redraw = True
        End With

Please help. Thanks!