You can get the address of a range like this Range("B2:D2").Address
This will produce an absolute range $B$2:$D$2
You can give pass it True/False to get relative addresses Range("B2:D2").Address(False, False)
Which produces the range B2:D2
Here is an example:
Dim TotalRows As Long
Dim i As Long
' Get the total number of rows in the current sheet
TotalRows = ActiveSheet.UsedRange.Rows.Count
' Iterate through all rows
For i = 1 To TotalRows
' Set the current cells formula range to Bi:Di where i = the current row
Range("A" & i).Formula = "=SUMIF(" & Range("B" & i & ":D" & i).Address(False, False) & ", 1)"
Next
Alternatively you can set the formula of a range like this:
Range("A1:A4").Formula = "=SUMIF(B1:D1,1)"
Excel will automatically increment the range based on the row for you.