Find Function Not Working

I have a worksheet with dates on and have user form to display dates within a range. I have created some code, but the find function errors and says it cannot find this value on the sheet, but it is definatly there. This is my code: I have added an asterix to where it errors and says it cannot find the value

Code:
Private Sub SearchButton_Click()
Dim lbtarget As MSForms.ListBox
Dim rngSource As Range
Dim FoundFrom As Range
Dim FoundTo As Range
With Worksheets("Calender")

[code]....