Byref argument type mismatch

Function Factorial(n As Integer, f As Integer)
f = 1
For i = 1 To n
Do
f = f * i
End Function
Private Sub Command1_Click()
Main.Visible = True
f1.Visible = False
End Sub
 
Private Sub Command2_Click()
Dim k1, n1, f1, f2, f3 As Integer
Dim res As Double
k1 = Val(Text1.Text)
n1 = Val(Text2.Text)
Call Factorial(n1, f1)
Call Factorial(k1, f2)
Call Factorial(n1 - k1, f3)
res = f1 / (f2 * f3)
Text3.Text = res
End Sub
 
Private Sub Form_Load()
Text1.Text = ""
Text2.Text = ""
End Sub

Call Factorial(n1, f1)

Dim k1 As Integer
Dim n1 As Integer
Dim f1 As Integer
Dim f2 As Integer
Dim f3 As Integer
Dim res As Double
k1 = Val(Text1.Text)
n1 = Val(Text2.Text)
Call Factorial(n, f1)
Call Factorial(k, f2)
Call Factorial(n - k, f3)
res = f1 / (f2 * f3)

Private Sub Factorial(n As Double, f As Double)
f = 1
For i = 1 To n
Next i
Do
f = f * i
Loop
End Sub
 
Private Sub Command1_Click()
Main.Visible = True
f1.Visible = False
End Sub
 
Private Sub Command2_Click()
Dim k1 As Double, n1 As Double, f1 As Double, f2 As Double, f3 As Double
Dim res As Double
k1 = Val(Text1.Text)
n1 = Val(Text2.Text)
Call Factorial(n1, f1)
Call Factorial(k1, f2)
Call Factorial(n1 - k1, f3)
res = f1 / (f2 * f3)
Text3.Text = res
End Sub
 
Private Sub Form_Load()
Text1.Text = ""
Text2.Text = ""
End Sub