Looping- Loop To Force A New Date Install Via A Input Box

The code below first asks a user to input a weekending date (which must be a Saturday). The value of the input box goes to cell C1 of my spreadsheet. That part works fine. I also have a function in Cell G1 with the function:


=TEXT(C1, "dddd")
I don't know if this is the best way to test for a Saturday but it is what I have,

Where is goes bad is if the date is not a Saturday. I have a loop to force a new date install via a input box but it won't update C1 with the inputed data to recheck for the Saturday value. Below is the whole code I am working with...


Dim aa As String
Dim bb As String

If Range("C1") = "" Then
Do While bb = ""
bb = InputBox("Please Enter a Weekending Date!")
Loop
Range("C1").Value = bb
End If
If Range("G1") "Saturday" Then
Do While aa "Saturday"
aa = InputBox("Weekending Must Be a Saturday. Please Enter a New Weekending Date")
Loop
Range("C1").Value = aa
End If