Match Date Passed To Variable

In my excel sheet, I have date values stored in cells from D7 ti IV7. in cells C8 to C100, I have a data validation which selects the values from cells D7 to IV7. When user selects a particular date in coumns C8 from the list, using my code, I am trying to search for the value stored in cell C8 within the range D7:IV7 using function Application.Match

While running the code by clicking on "Distribute Budgeted Efforts" command button, I am getting an error "Type Mismatch" and error is coming from code line number 27 which is "lInitial = Application.Match(lInitialdate, Range("D7:IV7"), 0) - 1"

My code is as below

Private Sub cmdEffortDistribute_Click()
Dim lCount As Single
Dim lStartDate As Date
Dim lCounter As Single
Dim lBudget As Single
Dim lInitial As String
Dim lInitialdate As String
Dim lInitialWeek As String

I am also attaching excel sheet which I am using here for reference.