Dim sDate
If the format of the date in your report is truely a date, you'd format it like: (my date control is a masked edit box)
sDate = "Date(" & Right$(mskDate.Text, 4) & "," &
Left$(mskDate.Text, 2) & "," & Mid$(mskDate.Text, 3, 2) & "

"
If it's a string in your report, you'd format it like:
sDate = Right$(mskDate.Text, 4) & Left$(mskDate.Text, 2) & Mid$(mskDate.Text, 3, 2)
Then pass it like:
ReportName.ParameterFields(0) = "Date;" & sDate & ";TRUE"
Where Date is the parameter name.