retrieve textbox value for editing

[jeck32]

hi guys,
i have a userform with a combobox linked to a vlookup for different currencies. now, once lets say GBP is selected, it would return the current exchange rate to USD in labelbox1.
now, i have multiple textboxes for entries, and whatever value i enter in the textbox it would return its value in my selected currency, and this table would be shown in a listbox.

now, if i would like to edit the value in the textboxes, i can select it from the listbox and edit the values in the textbox and save the changes via commandbutton. updating the textbox values should update the conversion too.
right now, i am getting an overflow error, please advise

i have the the sample code in my textboxes:
Private Sub totaTxt_Change()
dim PackLbV as single

PackLab.Caption = Val(totaTxt.Text) / Val(label1.Caption)

PackLbV = Format(PackLab.Caption, "00.00")
PackLab.Caption = PackLbV

and for the listbox

Private Sub ListBox1_DblClick(ByVal Cancel As MSForms.ReturnBoolean)

Me.IDCounter.Value = Me.ListBox1.List(Me.ListBox1.ListIndex, 0)
Me.totaTxt_Value = Me.ListBox1.List(Me.ListBox1.ListIndex, 2)